Author Topic: CB750 AHRMA Sportsman 750 Racer  (Read 177697 times)

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Offline Tintop

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #925 on: July 30, 2019, 07:50:24 PM »
Interested to know if your adjustment issues disappeared / lessened with Dennis' parts and the rebuild.

2nd Brian's comments on clutches; we always carried a complete spare with the my sidecar.
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Offline slikwilli420

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #926 on: July 31, 2019, 07:12:16 AM »
Thanks for the kudos guys, its awesome to have race fans all over. OS delivered in a big way with that clutch to get me going again. I will run that clutch this weekend and then maybe try a Barnett wholesale with springs and plates and see what that does. I will definitely have the back up clutch available as part of my spares. I really need to up my spares game for trackside fixes like this.

The clutch from OS adjusted perfectly per the manual and didnt seem to loosen at all over the course of the race. Clutch action was precise and flawless all Sunday, a new feeling that was very welcome. Upon disassembly of the other clutch, we noticed a witness mark on the back of the steel piece that the adjuster rod goes through where it was touching the center of the pressure plate bearing. I did also notice that the cover would not sit flush to the cases without the gasket as it should. I wonder if the AFM gasket I was running compressed enough over time that the very slight clearance that was there disappeared, causing interference with pieces that should not be touching. I really should get 2 sets of Barnett clutches with springs and good steels and set both up with the exact same front/rear backing plates and pressure plate and have it all ready to go in an oil bath, making for quick changes at the track.

Ill see you trackside this weekend Sean!
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
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AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
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Offline dunc

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #927 on: July 31, 2019, 07:19:38 AM »
You will have at least one more fan at gingerman...see you then Matt

Make that two!
it's amateur hour somewhere.

Offline bwaller

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #928 on: July 31, 2019, 05:51:31 PM »
Matt, I would stick with stock clutch parts. Maybe use Barnett springs if you feel new stock springs aren't up to the task. Stock gaskets, cables too.

For sure I'll get flamed for this but I never had good luck with Barnett clutches.

Offline kmb69

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #929 on: July 31, 2019, 06:26:11 PM »
Plus 1 on the sans Barnett friction plates.
Springs OK. Plates no.

Offline bear

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #930 on: July 31, 2019, 06:45:16 PM »
Plus 2,  Honda fibers for consistent feel and reliability for me.
Allways found Barrnett too snatchy off the line with not enough feel.

A  fully assembled spare clutch can bite you one the bum.
If they sit for awhile in your kit they can have a tendency to stick when installed.
I have been caught out  with this more than once.

Cheers,
Brian
The older I get the faster I was.

Offline dragracer

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #931 on: July 31, 2019, 07:14:59 PM »
Barnetts definitely done work for drag racing. Stock clutches for me all the way.

Offline hondaron

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #932 on: July 31, 2019, 07:58:06 PM »
Want to look you up at Barber, as we've been last 4 years.....

So clutch issue you had was Cycle X 4 plate clutch?

I've got that in my street bike, 76 with 915 motor and been really happy with it, of course not like on the race track 😊

Cheers,
Ronnie

Offline scottly

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #933 on: July 31, 2019, 08:14:44 PM »
I also was wondering if it was the 4 plate clutch.
Don't fix it if it ain't broke!
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Offline MessnerMoto

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #934 on: August 01, 2019, 02:01:08 AM »
I actually read all that text and enjoyed it ;) I envy you for your adventure :)

Offline MRieck

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #935 on: August 01, 2019, 06:08:33 AM »
Matt, I would stick with stock clutch parts. Maybe use Barnett springs if you feel new stock springs aren't up to the task. Stock gaskets, cables too.

For sure I'll get flamed for this but I never had good luck with Barnett clutches.
I 5th that.
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Offline Rocketman

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #936 on: August 01, 2019, 06:12:44 AM »
Congratulations on your podium finishes!  Way to persevere. Sounds like you are getting a handle on the clutch issues. For what it is worth, I have used Barnett plates and springs in my 550 since day one.

Best of luck at Gingerman.

Offline slikwilli420

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #937 on: August 01, 2019, 06:33:52 AM »
The issue arose at Barber last year, where I was running a stock Honda clutch, new fibers from Honda with good used steels, and fresh Honda springs. It came out of nowhere as the clutch had been flawless for the whole season leading up to that. I ran the same clutch for the first few races this year as I had no real solution to deal with the issue.

I swapped in Kenny's 4 plate system for a track day a few weeks ago to make sure it was good to go for RA. At Road America I was still experiencing the issue, but to a lesser extent than before. I found that only partially disengaging the clutch worked better than either clutchless upshifts or full clutch pull shifts. I had about 10 laps of track day time, 5 practices at RA and most of one race before it was cooked. With the lever losing adjustment after each ride I think I probably over-adjusted the lever to make up for the slack and it kept the plates from fully engaging, leading to a burned clutch.

I have the clutch from Dennis in there right now and Kenny is going to look over my 4-plate with the inner and outer hubs just as it came out to see what he can find. I have a spare in my toolbox, but that is the one where the problem originated from. The current clutch seems to be doing everything as intended and Ill definitely be pulling both after this weekend and comparing stack heights and inner/outer hub specs to make sure they are the exact same. I will likely swap in the Barnett springs, as before I was running the stockers with shims behind them for a little more clutch grip. Could the shims be the issue??

I switched from Rotella to Motul 5100 over the offseason hoping it would help and just to run a higher quality motorcycle oil but that change did not coincide with the clutch issues.
All you gotta do is do what you gotta do.

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AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
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Offline bwaller

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #938 on: August 01, 2019, 08:15:47 AM »
Is it possible it was adjusted too tight? Sorry Matt, I haven't looked back through your posts, maybe this question was answered.

Is it an OEM cable? Just be sure to use oil with a JASO wet clutch rating.

Offline bear

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #939 on: August 01, 2019, 08:41:48 AM »
If adjustment problems are discounted.

Another possibility may be damaged steels.
Either warping or hot spots.

Cheers,
Brian



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Offline slikwilli420

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #940 on: August 01, 2019, 08:42:24 AM »
Is it possible it was adjusted too tight? Sorry Matt, I haven't looked back through your posts, maybe this question was answered.

Is it an OEM cable? Just be sure to use oil with a JASO wet clutch rating.

Seems that what happened was the clutch was adjusted cold per the manual, and after heating up the lever would loosen significantly. At that point I would adjust the lever to take up some (but not all) of the new free play. I may have pushed it too far in that regard. The real issue is that its happening at all and there must be some stacked clearances that are causing my issue. Current setup is a Barnett cable and stock Honda clutch, with Motion Pro generic clutch perch/lever.
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
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AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
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Offline slikwilli420

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #941 on: August 01, 2019, 08:46:34 AM »
If adjustment problems are discounted.

Another possibility may be damaged steels.
Either warping or hot spots.

Cheers,
Brian

Could warped steels cause a change in clutch lever free play between hot and cold? Thinking more about how each part interacts with one another in the clutch, the steel part that has the three ramps for the balls and holds the adjuster bolt had witness marks from touching the center of the pressure plate bearing. I think now that if heat caused the parts to grow just enough (clearances between parts too close) that the parts touched it could throw the lever to the loose side of adjustment. If too close, even cold the adjuster bolt housing may have been touching the throwout bearing, keeping the lever on the clutch housing from rotating all the way down. That may all be bullsh*t but something was causing the huge swing in clutch lever free play and now it seems to have subsided.
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
Rickman CR Parts Kit Refresh: http://forums.sohc4.net/index.php/topic,154837.0.html
AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html

Offline bear

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #942 on: August 01, 2019, 09:35:43 AM »
If the steels have overheated at some stage any warping or hot spots may have increased the nominal thickness of some steels.
This could cause the clutch stack to increase in height.
The clutch is then adjusted (cold), the motor is run up to operating temp. (or better) and the softer hot steels are compressed  back into shape and the overall stack height is reduced.
That could result in a loose clutch leaver.
As the motor cools down after use the opposite effect is possible.

How's that for a theory? ;D

Cheers,
Brian

 
   
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Offline slikwilli420

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #943 on: August 01, 2019, 09:39:57 AM »
If the steels have overheated at some stage any warping or hot spots may have increased the nominal thickness of some steels.
This could cause the clutch stack to increase in height.
The clutch is then adjusted (cold), the motor is run up to operating temp. (or better) and the softer hot steels are compressed  back into shape and the overall stack height is reduced.
That could result in a loose clutch leaver.
As the motor cools down after use the opposite effect is possible.

How's that for a theory? ;D

Cheers,
Brian

 
 

The lever certainly does tighten up after the engine cools so that makes sense. I guess I need to check the flatness of my steels.
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
Rickman CR Parts Kit Refresh: http://forums.sohc4.net/index.php/topic,154837.0.html
AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html

Offline Old Scrambler

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #944 on: August 03, 2019, 03:00:05 PM »
Matt..........waiting for results from your 'home-track'..............The OEM K4 clutch springs I gave you have very few hours on them. I used RED Barnett springs with that basket and all was well.

Will look you up at Barber in October.
Dennis in Wisconsin
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Offline slikwilli420

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Re: CB750 AHRMA Sportsman 750 Racer - RA Update
« Reply #945 on: August 05, 2019, 08:26:44 AM »
Back to work after the short drive home from Gingerman Raceway about an hour away. The weekend went smoother than last weekend (no crashes) but that doesn't mean I didnt have to turn some wrenches along the way.

I got to the track Thursday night to set up base camp and get ready for the weekend. I was in high spirits for the weekend despite clutch issues and a crash at RA the weekend prior. With camp set, I connected with a few friends, new and old, then off to bed, albeit too late for me, around midnight.



Pure Honda sex, three ways:



Friday came early as they often do when you wake up with the sunshine at around 7am. Im up, the bike looks good, I grab my tech form and 10 minutes later Im back in the pits, ready to make it a great day. Im still running my RA gearing (17/46) which is what I ran at Gingerman last year so I use that as my starting point. It was hot all weekend, in the low 80's but with brutal humidity and relentless sunshine to keep the fresh tarmac in the pits nice and hot.

I got into the 1:54's last year during the races, and I was thrilled to find that the first practice out I was pulling down the same lap times. Its funny, I felt like I was just out there getting the feel for the track back, and I best my lap times from last year. Things are looking up. The second practice came, and delivered even better results, 1:52.6 this time. I came back from practice and checked tires, then noticed that my cam chain tensioner was a little weepy without. I wiped it up and snugged the screws. After lunch I was back at it, as I wanted to get all 4 sessions in for the day. Session 3 felt a bit slower and it showed in lap times, with a best of 1:55. The last session got me back into the mid 1:53's. With practice over for the day I noticed more weeping oil from the tensioner. I decided to pull it and put some Hondabond on the gasket for a nice seal. As I pulled the tensioner our, I noticed a shredded rubber nub where the steel foot should have been. NOT GOOD. I knew I had a few spares back at home which was under an hour away. Ashley and I loaded up, left our son Jackson with his aunt and uncle, and set off for home. I grabbed a spare tensioner from a stock motor, a spare oil filter, oil and a few other items and was back on the road headed toward the track. I got in around 9pm on Friday night and got to work. I was planning on pulling the exhaust, belly pan and oil pan to extract the metal foot on the end of the tensioner, but decided to stick my finger in the tensioner tunnel first to have a look around. Well the foot was just sitting there, resting against the back of the chain follower. Quick work with a magnet had that extracted and I was ready for the spare part. Dab of Hondabond and it was applied, then adjusted per the manual. Off to bed, but not before some beers, delicious food and camaraderie with fellow racers.

Saturday, race day, up at 7am to the sound of bikes and generators, and smell of race gas. I plan to hit both practices in the morning just to stay sharp for the race. I decided to do a swap from a 46 rear sprocket to the 48 to get a little more grunt out of the corners. I finished in time to get both practices on the new gearing. I ran 1:54 in the first session, and grabbed a 1:51.9 on the second session. Im running personal bests in practice and still feel like I have more to give. Things are looking good for the race. I was race 13, so the very end of the day. It was hot, and we had been waiting all afternoon to get to it. I have enough points to line up on the front row, right next to the current and past champions of the class.

I make my way around the track for a warm up lap and line up on the grid. We are in the second way so we watch as the first wave takes the green, then its our turn. I get a pretty solid launch and fall into 3rd, tight behind the two fastest guys in the class. My goal is to keep them close as long as I can, though both guys had been running stronger times than my best but I knew I would have some more during the race. My uncle (past champ) was running second behind my cousin (current #1 plate) and he botched a downshift into turn 3 on the first lap. I was there to take advantage and cut under him as he ran wide through the turn. I led him through the rest of the lap and as I climb the hill out of T10, I get into tuck. Just as I crest the hill, wide open, I see the whole field in front of my slowed on the track, red flag out at T11 and everyone funneling back to the pits.  Apparently there was two incidents behind us, both involving guys from our class getting wrapped up in guys from other classes. One resulted in a quick, but uneventful off track excursion for a fellow racer, but he was able to keep it upright and blend back onto the track. The second guy from our class took a really hard fall, tearing his bike up and suffering injuries severe enough to get an ambulance ride to the trauma center. I hear he is OK, albeit sore and pretty busted up.

We were in the pits about 10 minutes before we went through calls to the grid again, and made our way onto the track. We now had 6 laps to run the race. Again, I got a good (for me) start, but not as strong this time, and I found myself in traffic with a couple different guys. My uncle and cousin pulled away faster this time, and I settled into 3rd again. After a few laps, I started to feel like I had a stalker, as I could just hear the exhaust note of a vintage twin rumbling behind me. He eventually caught me and made a move to pass me as we approached a slower bike from the first wave. It took me a few turns to get around the slower rider and continue to pursue the new 3rd place ride. Ted was the rider, and has been racing and wrenching longer than I have been alive, and is a hell of a racer without a doubt. He was the guy to beat when my uncle started racing. I worked him over for the rest of the race, trying to show a wheel and get a run. I could reel him in at certain parts of the track, and he would pull me in other places. In the end, it was the hardest I had ever ridden and he beat my by half a second at the line. I crushed my personal best at this track with a 1:49.724. I got into the 1:50's, no easy feat for this class on this track. It was a great battle on a guy just a little better than me and he pulled me faster than I every thought I could go, but I know I can be even faster, smoother and smarter. That all comes with seat time.

The Saturday night awards was lively and fun, and it was great to see the guys get their wood for all that hard riding during the race. I wanted mine, I had to have something for Ted on Sunday. Wood at the home track was the thing I wanted all weekend.

On Sunday, my practice was more leisurely, delivering only 1:57 for lap times, but I wanted to save mine for the race. I noticed the clutch slipping at high RPM's as I climbed the hill from T10 heading to T11, so I decided to let the engine cool and put the shims behind the clutch that I had with Kenny's 4 plate kit to give the springs some extra preload. I got another pretty good launch and fell into 3rd place again, but I knew Ted would be hunting me all race. About half way through he showed a wheel into t3 (I think that's where it was) and he was in front. I spent he next lap watching him ride and seeing his lines. We came upon the same slow rider from the other class that we had on Sunday, but this time Ted was leading. I did the same thing he did to me on Saturday, found an opening and took it, overtaking Ted and the slower rider in the process, putting me back in 3rd, but I knew he would have something for me. I take the white flag in 3rd, feeling the fatigue of waiting all day then racing my heart out in search of Gingerman wood. As I round T10 and climb the hill I switch to 4th gear and let the clutch out, nothing. Clutch in, gear shift up, nothing again. One more time and I find 4th gear just as Ted pulls up next to me, and I click into 5th. He takes T11 to the inside and I try to drive hard from the outside to keep my corner speed up. I pass in front of him and he crosses behind me, now he's on the outside and Im inside drag racing to the finish. From the corner to the checkers is short enough that instead of losing precious time with a quick upshift (especially given what had just happened) I screw it on in 3rd gear and pull more revs than I ever had but he managed to put half a wheel on me right at the line. Ted beat me by 0.026 seconds. 1:49.501 was my best on the day, and my new personal best for the track. I have never ridden harder than I did this weekend, and I think it really helped develop confidence and skill on the track.

Best shot of the whole weekend:



Crew chief, my son Jackson and me:



Start 'em young:



My 50 minute ride home was solo so I had time to reflect on the day, and the weekend. The bike needs a number of tweaks leading into my next round (Little Tally is just over 4 weeks away) but Ill be ready. Im going to give up (at least for now) on the stock clutch and go full bag on the Barnett and see what happens. I found my clutch lever getting loose after both races this weekend, despite not really doing it during practice.

To do:
New clutch
Oil change, with an oil pan drop
Cam chain tensioner leak
Change back to Avon tires to wear them out on the very rough Little Tally race surface
Lose another 10 or so pounds in my quest to be lighter and leaner

A big shout out to Duncan (dunc) and Sean (seanbarney41) for coming out to show support at the races! Duncan showed up to shoot old school film of some great vintage bikes. I cannot wait to see what pictures he took of Saturday's events.

33 days...
« Last Edit: August 05, 2019, 10:03:37 AM by slikwilli420 »
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
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AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: CB750 AHRMA Sportsman 750 Racer - Gingerman Update
« Reply #946 on: August 05, 2019, 09:19:15 AM »
CONGRATULATIONS!!!!!!
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline dragracer

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Re: CB750 AHRMA Sportsman 750 Racer - Gingerman Update
« Reply #947 on: August 05, 2019, 09:38:31 AM »
Good job. Nice race report. I felt like I was right there with you.

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Re: CB750 AHRMA Sportsman 750 Racer - Gingerman Update
« Reply #948 on: August 05, 2019, 10:09:19 AM »
Congrats on the exciting racing and fantastic lap times!  Hope you can sort out the clutch issues and figure out what went wrong with the missed shift/gear.
Great write up.
David
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Offline slikwilli420

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Re: CB750 AHRMA Sportsman 750 Racer - Gingerman Update
« Reply #949 on: August 05, 2019, 10:14:30 AM »
Congrats on the exciting racing and fantastic lap times!  Hope you can sort out the clutch issues and figure out what went wrong with the missed shift/gear.
Great write up.
David

Thanks David. Seems to me that something is expanding in the extreme heat of racing and that is causing the lever at the clutch cover to turn slightly, introducing extra free play at the hand lever. Only of of two things (as I see it but correct me if I am wrong) is the steels or the fibers.

Despite people being happy with Honda steels and fibers, Im thinking a wholesale swap for Barnett would be a good idea. Then I won't have to deal with shimming the stock springs for more pressure and the Barnett should take a good beating.
All you gotta do is do what you gotta do.

Vintage Speed Parts Mashup: http://forums.sohc4.net/index.php?topic=133638.0
Rickman CR Parts Kit Refresh: http://forums.sohc4.net/index.php/topic,154837.0.html
AHRMA CB750 Racer: http://forums.sohc4.net/index.php/topic,158461.0.html
AHRMA Superbike Heavyweight Racer: http://forums.sohc4.net/index.php/topic,173120.0.html
'76F CB750 Patina Redemption: http://forums.sohc4.net/index.php/topic,174871.0.html