Author Topic: CB750A Street ET bracket drag bike. A year to build it. (Read 621946 times)

Bill/BentON Racing · « **Reply #1075 on:** April 12, 2011, 06:58:14 AM »

Quote from: SamCB750A on April 11, 2011, 11:00:09 PM

Quote from: dragracer on April 11, 2011, 08:59:38 PM
Wow, did everyone get scared to post on this thread??

I was mad busy all day at work Frank and although I was on line, I just didn't find time to post.
After work I realised I had forgot it was my Daughter in laws birthday and had to travel to the other side of town to deliver her birthday card. I posted as soon as I got home when the panic was over.

Sam

Sam,we know you ok posting,but I think we ran them off.To all reading,watching,supporting and offering advice,insight,and input,DON"T STOP!
Same rules apply to this thread as the normal forum posting,so PLEASE,post away,been too much fun,hard to read 47 pages,so ask,we'll let you know if we've already been there.Carb #1 in surgery,blockage appeared to be slag? Anyway we're attempting to repair,dynojet kit on order(thanks Big Jim)Want to go to dyno Sat. with the CV's back on! Yep,I believe!!!Jon's found some Canadian CB750 Nighthawk CV's 34mm!We're looking @ other CV options and going forward on project.So we luv you ,appreciate you and WANT your input!Team Sam Green/Bill Benton SAMAUTO will rock and roll!!It's got a Mike Rieck motor!!!

ivanhoew · « **Reply #1076 on:** April 12, 2011, 08:43:12 AM »

Quote from: bellcow54 on April 12, 2011, 06:58:14 AM

Quote from: SamCB750A on April 11, 2011, 11:00:09 PM
Quote from: dragracer on April 11, 2011, 08:59:38 PM
Wow, did everyone get scared to post on this thread??

I was mad busy all day at work Frank and although I was on line, I just didn't find time to post.
After work I realised I had forgot it was my Daughter in laws birthday and had to travel to the other side of town to deliver her birthday card. I posted as soon as I got home when the panic was over.

Sam
Sam,we know you ok posting,but I think we ran them off.To all reading,watching,supporting and offering advice,insight,and input,DON"T STOP!
Same rules apply to this thread as the normal forum posting,so PLEASE,post away,been too much fun,hard to read 47 pages,so ask,we'll let you know if we've already been there.Carb #1 in surgery,blockage appeared to be slag? Anyway we're attempting to repair,dynojet kit on order(thanks Big Jim)Want to go to dyno Sat. with the CV's back on! Yep,I believe!!!Jon's found some Canadian CB750 Nighthawk CV's 34mm!We're looking @ other CV options and going forward on project.So we luv you ,appreciate you and WANT your input!Team Sam Green/Bill Benton SAMAUTO will rock and roll!!It's got a Mike Rieck motor!!!

hi bill , i really enjoy your enthusiasm ,a rare gift !
i think the locked thread bit has everyone pretty confused and uber cautious .so its stopped any constructive input and analysis from others apart from the team ,who know what to say to who, to get on and not ruffle feathers .

its an enjoyable thread to read ,and personally i dont want to try to help again, only to upset .if you see what i mean .. id rather keep quiet and enjoy the vibe !

regards
robert

dragracer · « **Reply #1077 on:** April 12, 2011, 09:53:17 AM »

Quote from: dragracer on April 11, 2011, 08:59:38 PM

Wow, did everyone get scared to post on this thread??

Sorry guys but one of us had to ask that question. I sensed hesistancy from the other forum members to post so i felt it best to put the question out there hoping someone would have the balls to be honest- thanks Tintop for opening up the dialouge. Its not my thread but i feel it belongs to every forum member to post openly and freely since Sam posted his intentions to share build the project with us- of course i can't speak for Sam on this.

Ok guys, i personally feel like i've lost all the friends i've ever had. Please come home so we can play-lol. No more book burning allowed!!!!!!!!!!!!!!

Sam Green Racing · « **Reply #1078 on:** April 12, 2011, 11:49:34 AM »

Frank, not many people posted in any of the threads over the last few days.
Several forums I post on have all been the same, don't worry to much mate, even I have been quiet.

Sam.

MCRider · « **Reply #1079 on:** April 12, 2011, 01:53:54 PM »

Quote from: SamCB750A on April 12, 2011, 11:49:34 AM

Frank, not many people posted in any of the threads over the last few days.
Several forums I post on have all been the same, don't worry to much mate, even I have been quiet.

Sam.

Everybody's working on their taxes.

I love dragracing threads BTW. Hope to screw up the courage to take mine out.

voxonda · « **Reply #1080 on:** April 12, 2011, 02:04:51 PM »

Really love that Auto 750. Not much dragracing, that I know of here, Would like to have a go with the one, F2 engined, building now.
Keep up the good work and make us proud(er)!

Cheers, Rob

dragracer · « **Reply #1081 on:** April 12, 2011, 02:50:22 PM »

Quote from: MCRider on April 12, 2011, 01:53:54 PM

Quote from: SamCB750A on April 12, 2011, 11:49:34 AM
Frank, not many people posted in any of the threads over the last few days.
Several forums I post on have all been the same, don't worry to much mate, even I have been quiet.

Sam.
Everybody's working on their taxes. I love dragracing threads BTW. Hope to screw up the courage to take mine out.

Ahhh, taxes, i was feeling pretty good but now you've depressed me.

.

scottly · « **Reply #1082 on:** April 12, 2011, 08:38:04 PM »

Quote from: bellcow54 on April 10, 2011, 10:18:25 AM

So first run,a lot like before,way too fat,

A switch from CV carbs to smooth bores, with similar results? The smooth bores at WOT, low RPM should have been leaner than slow opening CV slides, due to the low velocity through the carb bores, which would provide less pressure drop=less fuel.
Sam, please don't lock the thread again; a simple "shut the F up" PM will suffice...

dragracer · « **Reply #1083 on:** April 12, 2011, 11:27:35 PM »

Stupid question; Whats wrong with using the stock carbs that came on the bike and rejetting them? Or was that mentioned in a previous thread? I don't remember that coming up.

I think i'll take a break from posting on this thread for a while myself. I'll wait til Jon and Mike decide to start posting again. They've turned into the missing links for some reason.

Bill, please let me know when and where you decide to test again.

Take care fellas.

Sam Green Racing · « **Reply #1084 on:** April 13, 2011, 03:24:24 AM »

OK guys, let me tell you my take on the problem.
1st. Due to the fact that the bike went quicker with each run (it did run slower when temperatures soared from mid day to mid afternoon) it is plain to see that the motor is still a little tight and might not be releasing enough power low down to spin up the modified converter.

2nd. It could be the cam that I (me) chose has moved the low down power/torque away from the bottom end a little to far.
I could be wrong but until the motor is fully run in and has stopped improving with every run, until that time, we can't even start too look at what might be wrong. Until that time comes, I'm afraid it's all just speculation.

OK, so why this modified converter and this particular type of CV carbs, well to put it in a nut shell, these two components have been tried and tested over many many years and have been proved to work best irrespective of what anyone might think and for people to tell the guy that figured all this out what he MIGHT be doing wrong is very hurtfull, hence no more post from our auto guru.

Moving on to the carbs. With conventional carbs, when you whack the grip round fast, the slide goes up letting in loads of air and the needle comes out of the main jet letting a big dollop of fuel through. At this point, the motor will cough and gas up or at best it will clear and the revs will go to maximum. All this will happen in about a one and a half seconds. On the auto, we don't have that one and a half seconds. If the throttle is opened to soon, it will boil the oil and ruin the dial in time, put on to late and you've lost the race. With the CV carbs, the motor only takes in what it needs for a quick but progressive climb to wide open throttle but bare in mind, this is done against the converter that is trying to stop you from doing it.

If you want to see what it feels like to launch an automatic, try this. Take your 750 K or F and set tickover to 2,500rpm. With your right foot hard on the back brake, put the bike into gear and slowly come off the clutch until the revs drop to 1,000rpm.
THIS IS WHAT IT FEELS LIKE IN STAGE. Now go to WOT and hold for three quarters of a second and then come off the brake and clutch at the same time.

well what are you waiting for.

Sam.

jweeks · « **Reply #1085 on:** April 13, 2011, 05:06:37 AM »

Sam,
Yes, I'm still here. Got nothing much to add at this time. Just waiting to see what happens Saturday on the dyno.

Dragracer,
Stock carbs suck. The idle circuit uses the main jet for getting the idle circuit fuel. Take away the stock air box, modify the motor, and you'll need more fuel through the carbs. Give the carbs bigger main jets to satisfy the need, and the idle circuit goes very rich. Once you're past the idle end of the rev range, it can run fine. Getting to midrange will be slow. As Mike stated, get the A/F ratio right before we look elsewhere. I'm not good enough to rework passages on the stocker carbs to relean it out. Hondamatic drag bikes spend a lot of their time on the idle circuit in the pits and staging lanes. Stock carbs that I have run (yes, the clutch K versions that are 2mm bigger than the automatic ones) foul plugs due to the long idling periods. This makes for inconsistencies. Bottom line, they just don't work well in this kind of an application.

Don't pick on the 29's tried last weekend. They weren't set up properly. They can work OK if they were given the needed Dyno time to sort out the A/F ratio throughout the rpm range. Their only short coming is that they take a little more time to rev up when you open the throttle. Whacking open the throttle with those carbs will not always just pull cleanly up in the rpm range under load. They like to be rolled open a little slower. Yes, I've run those carbs before as well.

I'm working on getting my own Hondamatic ready for this season's racing. 811cc, ported head, mild cam, and Canadian Nighthawk 34mm CV carbs that "should" bolt up. Not going to be a looker like this one, but may get to 60' quicker than one down south...

Bill, I'm working on my end of the same situation. I'll be on the dyno up here to find what the bike wants.

Like everyone else, I'm trying not to offend anyone. Sorry if I have.

Hondamatic

Bill/BentON Racing · « **Reply #1086 on:** April 13, 2011, 01:02:56 PM »

Jon,thanks for the response.We're all in this together(as Big Jim said,group hug).Glad to read your post.Mike's right,until we get correct A/f we don't know what we got.....well I do know we got one hell of a motor.Jon's correct on 29's,no time to tune(no test and tune @ track like usual),but we have good news,Mr French found extracted ,cleaned out passageway,rewelded,drilled etc.#1 is going to work,hope we have them on by Sat.Dragracer.......Gladys said you better post or no more .000 reaction times! ;)Mike,let us know about spacing on 93 Nighthawk carbs and bore size.Thanks,for checking and that sweeeeeeeet motor! I just fired it up,Jim we need an audio of it!

Leathers arrived yesterday,better reaction time come with them? If we can't dyno CV's, on Sat.we're dialing in the 29's!

Ya'll stay in touch,we will DO IT!!!

,Bill

voodooracer · « **Reply #1087 on:** April 13, 2011, 01:45:20 PM »

Bill, look for the "inspected by inspector # xxxx" in the pocket. Just move the decimal point around to get your reaction time!!
Glad I could help.
Whew!, this is hard work!
I need a beer now.
I mean,
I need a BEER!!! NOW!!!
Keith L.

Bill/BentON Racing · « **Reply #1088 on:** April 13, 2011, 02:14:25 PM »

Keith,great to hear from you,I need 2 beers ,been to dentist again!Wanna see Chainsaw tearing up the strip soon.Still gotta work on clutch? Good Luck and keep at it!

,Bill

Sam Green Racing · « **Reply #1089 on:** April 13, 2011, 02:18:13 PM »

Good luck from me to Keith, I'm having a beer with ya.

or 2 or 3.

Sam.

Jim F · « **Reply #1090 on:** April 14, 2011, 08:48:52 AM »

I will post the pictures as soon as I am back in the shop
Very interesting

Jim F · « **Reply #1091 on:** April 14, 2011, 04:58:41 PM »

I will post the pictures as soon as I am back in the shop
Very interesting.

Ok I am back

As some of you know the CV carbs that we have been working had a slight problem with #1 carb
bottom was very lean. So much so that the #1 header was turning a very pretty blue. Thats not good
So when Bill put on his 29 smooth bores, I took the CV,s back to my shop and put them under the microscope
What I found was some or it looks like casting slag or something left over from the machining process inside the
passage from the back side of the air jet. It was very hard as a drill would not go threw this although the drill did go threw the side wall
This is not bad because I was able to see what was blocking the passage, I got it cleaned out, welded up (Micro Laser welding) remachined the passage.
Drilled out the remaining air jet, ordered a new stage 3 kit from dynojet and all is good
check out the pictures as this one is for the books
I have never seen this before but life sure is interesting

ok here ya go

Jim F · « **Reply #1092 on:** April 14, 2011, 05:05:01 PM »

pictures of the carb work

This first picture is where the drill took a so called turn

The second is looking threw the microscope of my laser system and looking down at the bottom
of the pa sage way and starting the welding process

The third the the finished product
I still need drill out the jet to match the others but will do that before I install it in to the carb body

I am now micro polishing the bores and slides but not too shinny
re assemble and see what we have

Jim

bwaller · « **Reply #1093 on:** April 14, 2011, 07:01:30 PM »

Good work Jim, very tidy fine welding. I hope every little bit helps the outcome.

jweeks · « **Reply #1094 on:** April 14, 2011, 08:10:18 PM »

Very nice work. Will be interested in what diameter the plugs from the jet kit are drilled/molded to!

JW

I offered Sam to buy back the carbs for what he paid for them before this work. I ran them for a season with an old exhaust header. I didn't spend much time on the idle circuit, since the pipes didn't show much except rust...

Jim F · « **Reply #1095 on:** April 15, 2011, 06:20:00 AM »

Hey John
The plugs are tapered from .162 to the big end at .175 I drill and reamed the hole to .170 for a good interference fit.
The air jet is .040

Sam Green Racing · « **Reply #1096 on:** April 15, 2011, 06:33:29 AM »

Nice precision work Jimmy,

when will they be ready to try again ?

Sam.

Jim F · « **Reply #1097 on:** April 15, 2011, 07:31:08 AM »

I will have the jet done today but I will do some polishing on the slides and bore over the weekend.
our next trip to the dyno should tell us what we need to know. Bill
and I are going tomorrow for the smooth bores
call me if needed or I can call you but i need your number

Jim
770-367-7320

Sam Green Racing · « **Reply #1098 on:** April 15, 2011, 07:41:46 AM »

Try to get me on Skype around 4pm your time, much cheaper

My home phone is 0161 775 0071.

Sam.

jweeks · « **Reply #1099 on:** April 16, 2011, 03:58:10 PM »

Bill will have a post soon with the dyno results. A couple of trips to the dyno gained 6 horses on the top end and over 10 in the midrange. The bike slips the torque converter to a higher rpm on the starting line. We've got more improvements coming. This is why I was so happy to get this combination on the dyno. I always run my Hondamatics on the lean side. Samauto is finally getting closer to what I would be running. Sam's going to have an ATM!

JW

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Author Topic: CB750A Street ET bracket drag bike. A year to build it. (Read 621946 times)