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Author Topic: Let's go roadracing...continuing saga  (Read 85625 times)

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Offline bwaller

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Let's go roadracing...continuing saga
« on: February 16, 2011, 06:33:55 pm »
I'm pretty sure some guys here fiqured I wasn't building a race bike at all and gave up on me.  ::) Well for what it's worth I'd like to show a few pics of what I've been up to. This is more a picture thread than a build thread as it nears completion, but please throw suggestions or insults or whatever and I'll either take heart or play ignorant.  ;D  The 750 guys may roll their eyes at yet another 500, but here goes anyway.

First let me mention I need to give thanks to this place for many ideas, and especially MRieck, turboguzzi, Kayaker, and just lately Voxonda.

Some of Mikes handiwork, and we decided on OEM valves.

Exhaust




Intake




With this small chamber I'm going to try pulse type coils from a dohc750. I have a set of 3 ohm Dyna's that I'll test too for comparison once on the dyno.




I made up a set of manifolds for Mikuni spacing with approx 9 degree incline to help straighten the intakes much like TG did earlier. Just to show the difference compared to the "S" shape of the originals. This shot is through Mikuni VM28's and stock PD's.







Kibblewhite guides & springs and seat pressure of 75lbs. Extra shimming was needed so installed height was just under Kibblewhites suggested 1.38-1.4" but feel the pressure most important.





I had 60mm pistons made to use Honda's VF500F thinner 1mm compression rings. Designed the dome for 12:1CR, squish is 0.9mm. The pistons are forged and a bit porky @ 195 grams (piston/pin/rings/2 clips) Stock 750 piston (#300) of 61mm is 220 grams. I searched everywhere for tapered wrist pins and in the end machined a taper in CBX1000 pins which are fairly thick walled (0.116") so should be very strong. Finished weight 38.2 grams from CBX 44.4 original.






 
« Last Edit: April 19, 2013, 06:05:50 pm by bwaller »

Offline bwaller

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Re: Let's go roadracing...continuing saga
« Reply #1 on: February 16, 2011, 07:03:24 pm »
I had the rockers hardwelded then matched weights to the lightest. Decided on the Megacycle 126-20 and shortened a 750 HD Tsubaki camchain.








Something I probably wouldn't do again as it was a time consuming job. We made a CB360 6 spd fit the 550 cases, then had Ellis Moore make a new 16 tooth mainshaft as well as five other gears to tighten the ratios. As I mentioned before it's not Yoshimura stuff but considering 1st will be launch only I think the remaining five should be fun....if it doesn't blow to hell.  ;)

Final overall reduction is 56.3%, 2nd through 6th is 43.7%
 
1st  2.125:1
       1.65
       1.333
       1.111
       1.0
       0.929




One potential issue I see is that the c-shaft seal doesn't completely seat inside the case to accomodate the bearing needing to be moved outboard for enough gear space. As a result I made a seal retainer which puts pressure on the seal to hold it in place, fingers crossed. Using a CB650 oil pump.





Also used a deeper CB650 oil pan for added volume and followed CB500's lead and made a mount for a primary chain tensioner and then modified a 550 oil pickup.





I played with shimming the clutch center to make an eight friction disc clutch. I think there should be enough free play to work and also hope stock springs will be enough. If not I have some Barnett springs and will start exercising the left wrist!












 
« Last Edit: April 19, 2013, 06:06:46 pm by bwaller »

Offline Flying J

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Re: Picture Time
« Reply #2 on: February 16, 2011, 08:21:32 pm »
I love this aspect of the builds around here. Makes me wish i was into racing.  :-[ Ill take what i can and apply it to my street bikes.

Thanks for the pics.

Offline Doctor_D

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Re: Picture Time
« Reply #3 on: February 16, 2011, 08:27:23 pm »
Wow.  I am incredibly impressed.  :o

Not to worry you, but ine thing I want to caution you on is the thinner piston rings.  I went down this path with my Norton, making pistons that took 74mm 1.0, 1.2, 2.8 low-tension rings to reduce frictional losses.


I promptly ran into problems with repeated partial seizures.  Rings are the path for the cylinders to conduct heat away from the pistons.  Less surface area means the pistons hold more heat.  More heat means more piston expansion.  Too big a piston and it starts welding itself to the cylinder walls.


Thin rings work as advertised on watercooled motors, but have to be watched on aircooled bikes. Hope you don't run into the problems I did.
Take care,
David
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Offline scondon

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Re: Picture Time
« Reply #4 on: February 16, 2011, 09:00:51 pm »
Brent, it is work like this that makes me want to pitch it all in, sell the bikes and become a maple farmer. Experiments in engineering that are pure fantasy to a "bolt together" builder like me with limited tools and skills. And I mean that as a high compliment, of course  ;D




More pics please
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Offline FunJimmy

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Re: Picture Time
« Reply #5 on: February 16, 2011, 09:11:10 pm »
Great stuff Brent and nice presentation too.
Those pistons are the schnizin!
Where do I get a set?

FJ
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Offline Bill/BentON Racing

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Re: Picture Time
« Reply #6 on: February 16, 2011, 09:43:43 pm »
Wow,nice work Brent! 8).It'll be worth the time and $$$.Looks really well done,Congrats,Bill
Gotta dyno this puppy. ;) ;D
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Offline lordmoonpie

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Re: Picture Time
« Reply #7 on: February 17, 2011, 12:02:39 am »
Lovely stuff Brent, I can really appreciate the "what if" type of building you've done here, it's what keeps me interested in these bikes and your take on things is great inspiration from this great forum. Can't wait to hear it  ;D
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Offline bwaller

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Re: Picture Time
« Reply #8 on: February 17, 2011, 05:28:44 am »
Dave, I understand the concern, but was starting from scratch and preferred to use Honda rings. One successful racer in the US was pushing for me to find 0.8mm comp rings from a modern motocrosser but there weren't many 60mm options so these came partially by default. The pistons are low silicone content so will certainly grow in the bore. It wasn't an expensive venture so I'll see how it all holds up.

Jim, the pistons are Ross, around $100 ea. It took a lot of measuring and back & forth to get the right depth reliefs, height dome, etc. but my job card is available. I felt good when I found the Interceptor 60mm rings and bought a few sets. Then they were promptly unavailable.  :o The last time I checked nothing had changed, so sourcing different rings would be job one.

External lines


I wanted filtered oil for the cam but hate sourcing off the right gallery end, so finally welded up a boss, drilled & tapped for access right off the gallery in front of the oil pump. It's a safer location.








As a result of using a different countershaft and final sprocket position, plus a CB350 rear hub, sprocket alignment was a struggle. This frame is 78, the last year of production and it's obvious Honda's production tolerances were allowed to slide and things just didn't align. With the engine in the frame, I settled on a forktube in the crankshaft bore to measure back to the swingarm pivot and finally rear axle.

In the end the engine was offset 3.5mm to the right in the frame, plus removed the 2mm rear sprocket washer and further machined 1.5mm from the outside of the new 520 rear sprockets to proper sprocket alignment. This leaves only the circlip locating the rear on the hub but I'm sure that's fine.

If that wasn't enough of a head scratcher, the engine was cocked in the frame and besides the offset, different shims were welded onto frame bosses, and one boss ground, just to align the c-shaft and the swingarm pivot. Honda driving sprockets "float" for good reason, it's very smart way to attach them.




In the front I have one thicker alloy engine mount on the left and also replaced the rear right original steel offset bracket with a flat alloy piece. Another year I will install bushings in the engine mounts and final ream to take the slop out of mounts. These frames need the engine for support.








Here's a shot of my attempt at stiffening the swingarm. The X shaped aluminum bracket is fastened at four points using splined shoulder bolts that hopefully add strength.....otherwise it's just a support for the ignition box & battery.  ;D Did this first in the seventies, with only 6mm bolts and could see where the movement removed paint.  

The chain roller is also visible, Simon & TG are right, those little rollers won't last, but I have another plan to make something better.


« Last Edit: February 17, 2011, 09:08:09 am by bwaller »

Offline paulages

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Re: Picture Time
« Reply #9 on: February 17, 2011, 09:19:57 am »
Finally some pictures! Great stuff, Brent.

Couple thoughts, but I have to run out the door. Regarding the clutch, if your 8 disk conversion doesn't help, try the 650 gearing first... you'll have to correct the ratio at the final drive, but the difference in ratio between the primary and clutch allowed me to run stock clutch springs with no slippage.

The time you've spent thinking things through is very evident. Beautiful work!
paul
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Offline turboguzzi

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Re: Picture Time
« Reply #10 on: February 17, 2011, 10:38:52 am »
Wow, nice strip show, proper sohc sex  ;)

Wish my parts looked as good. But then, i am a known corner cutter :)

Not much there that i would do differently other than the whole engine offset thing, re-read that part and still don't get it..

Will be nice to see what she does on the dyno

When is the track baptism?

Keep the rubber side up and enjoy!

TG



 




Offline FunJimmy

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Re: Picture Time
« Reply #11 on: February 17, 2011, 11:15:14 am »
Keep the rubber side up and enjoy!

TG

TG
It might be a bit different on the other side of the pond, but here in Canada, we want to keep the rubber side down, and the shiny side up.
To each their own, I guess.  ;D

FJ
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Offline Howell

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Re: Picture Time
« Reply #12 on: February 17, 2011, 11:44:56 am »
Hot stuff , all is done very properly.
I am curious about the Dyno result.
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Offline Sam Green Racing

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Re: Picture Time
« Reply #13 on: February 17, 2011, 12:03:47 pm »
Brent, after seeing your other bikes, the racer is just what I expected.
You must have spent many many hours in your workshop to turn out that masterpiece. 8)
It must have been real tough on Debbie you spending all that time in there.....she is still with you, isn't she ?  :D :D :D :D :D :D :D :D I bet she's as proud of it as you are. ;)
Hope it goes as good as it looks and you have lots of safe fun on it. ;)

Sam. ;)
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Offline turboguzzi

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Re: Picture Time
« Reply #14 on: February 17, 2011, 02:10:04 pm »
Keep the rubber side up and enjoy!

TG

TG
It might be a bit different on the other side of the pond, but here in Canada, we want to keep the rubber side down, and the shiny side up.
To each their own, I guess.  ;D

FJ


Judging by how Brent's oil pick up works, i'd say i'm RSU and you are USD!

:)

Offline Sam Green Racing

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Re: Picture Time
« Reply #15 on: February 17, 2011, 02:16:22 pm »
Hey Yo, don't forget that you are half way to Australia to most of us, now that is USD. :D :D :D

Sam. ;)
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Offline bwaller

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Re: Picture Time
« Reply #16 on: February 17, 2011, 07:48:12 pm »
These engines have no crankcase breather. I know in a four cylinder pumping forces are negated but there is never a perfect ring seal. In order to avoid any extra bottom end pressure on my c-shaft seal I'm wondering about a 1/2" breather port in the e-start plug.

Any opinions? What about a check valve inline?

Paul, I'll keep the 650 primary drive in mind.

Sam, Deb is off curling so much winter evenings it's either work in the shop or sit at the pub for me.  ;) Come to think of it I'm not sure which costs less!

Offline Doctor_D

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Re: Picture Time
« Reply #17 on: February 17, 2011, 08:11:55 pm »
I like using an XS650 reed-valve type breather on virtually all of my motors.  Power brake check valves work pretty well too, but aren't as durable.

As you said, ring seal is never perfect, plus pulling a little vacuum in the crankcase is worth a fractional amount of power.
Take care,
David
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1971 Norton Commando

Offline turboguzzi

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Re: Picture Time
« Reply #18 on: February 17, 2011, 10:46:02 pm »
well, if you feel like spending more time in the shop you could try build a positive crankcase venting system using the exhaust flow to create low pressure. in use of many of the GP bikes.

built such a thing myself for the 500/4 but never got around to measure the actual negative pressure or hp advantage. it sure worked as it proceed to empty whatever oil was in the overflow bottle, creating a huge smoke cloud in the paddock! eventually removed as i wasnt quite sure that the tech guys would like all those tubes running back and forth that potentially could contain oil.  

Might give the idea a try again with the GPZ

And BTW, totally disagree with doctor d on ring thickness. No problems whatsoever with my 1.2mm and later 1mm rings in my pistons. Thinner rings will develop less flutter at high RPM = seal better = less leak and its a long going trend regardless of air or water cooling. 2V Air cooled ducs run just fine on 1mm -1.2mm rings too. Your seizure must have happened for some other reasons, IMHO of course. 

TG



« Last Edit: February 17, 2011, 10:57:33 pm by turboguzzi »

Offline Doctor_D

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Re: Picture Time
« Reply #19 on: February 18, 2011, 05:50:43 am »
And BTW, totally disagree with doctor d on ring thickness. No problems whatsoever with my 1.2mm and later 1mm rings in my pistons. Thinner rings will develop less flutter at high RPM = seal better = less leak and its a long going trend regardless of air or water cooling. 2V Air cooled ducs run just fine on 1mm -1.2mm rings too. Your seizure must have happened for some other reasons, IMHO of course. 

Where the facts are unclear, I'm fine with divergent opinions - so no offense taken.  :) It was a reasonable-sounding theory offered by my machinist and something I don't want to see happen to others.
Take care,
David
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Offline Tintop

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Re: Picture Time
« Reply #20 on: February 19, 2011, 06:57:19 am »
Great thread bw.  Always happy to see more pic's of ways to spend money on these CB's. ;) :) 

A Nova 6spd was originally part of the plan for the cafe, do like your 360 conversion however.  Maybe later.

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Offline haill

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Re: Picture Time
« Reply #21 on: February 20, 2011, 11:32:04 am »
Do you have one to share that gives an over-all view? The details are beautifully done and well thought out but hard to get a sense of the complete package your creating.
thanks. Keith

Offline bwaller

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Re: Picture Time
« Reply #22 on: February 20, 2011, 04:48:30 pm »
I'm not a machinist, but have some experience. Seeing what so many other guys are and have done building parts & bikes, I feel more like MacGiver than machinist.

I had these CB500 rotors reduced to 5mm and drilled. But OH-NO that wasn't enough, in a rotary table I cut the grooves, removed material between rivots and some drilling of the carrier. Final weight is just over two pounds less than the originals. Following TG's lead I'll use these small Brembos with 750F2/3 forks, Racetech emulators & springs, SS 20mm hollow front axle and Avon AM20 on an Excel WM3x18". Rear is a WM4 with a 350 twin hub and AM23 tire. Decided on using a modded brake rod.


 








I tried to come up with a strong option for rearsets, capturing a shortened GSXR bracket between two pieces of steel welded to the frame. In case of a crash hopefully these will mostly survive, levers excluded. The sprocket cover includes a needle bearing support for the shifter shaft.







Brake side is obviously the result of feeling my way along and finally deciding on a rod instead of cable. Not much to look at.





The seat is from Holland. (same as Howell's) With a short tank and wanting the rear cowl where it is on the frame, the seat needed to be longer. I made an aluminum base to sit above the frame rails 1" and glassed the seat to the base. Welded a 1" moly tube between the shock mounts and a couple aluminum hooks hold the seat rear. One bolt fastens the front of the seat & rear of the gas tank, so removal of either is a snap but still secure. Shocks are 14.25" Works Perf.











  


 
« Last Edit: February 20, 2011, 07:27:23 pm by bwaller »

Offline bwaller

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Re: Picture Time
« Reply #23 on: February 20, 2011, 05:23:35 pm »
The exhaust is Kerker. To clear the deeper 650 oilpan I made kerf cuts to lower the collector, then altered the exhaust elbow position so the mid pipe exits more from center underneath in an attempt to narrow the bellypan. I added 2" to the midpipe length plus cut the mega in half at the kink to change the angle and help tuck it in higher. I have two different size baffles to try on the dyno.




The bloody bellypan, it isn't pretty. It's all square and straight & 18 gauge, but it's about all I could do in my limited capacity. It needed to surround as I didn't leave room between oil pan & exhaust. The exhaust nearly touches under the collector and on the right rear exit out of the bellypan. Bottom is narrow in front, wider at the rear. I loaded the suspension to 80% and had ample ground clearance past the point of traction loss so it ought to be ok.









Still lots to finish so I don't have a good pic of a complete bike, trying to decide whether or not to use the upper part of a full fairing, the lower needs more time to fit than I have. I'm working on tuning what I can with suspension components while I wait for parts.

Told you it was picture time.







« Last Edit: February 21, 2011, 03:33:09 pm by bwaller »

Offline Bill/BentON Racing

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Re: Picture Time
« Reply #24 on: February 20, 2011, 06:30:51 pm »
Brent,excuse me,I'm drooling.Wow,what a 500/550.Beautiful my man!Worth the wait.I'm jealous,get that thing on the dyno and the track! ;)Man ,that is SOHC sex.You have outdone yourself. ;D.I wanna 8x10 glossy photo,and video and audio.Bill
BentON Racing Website
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Over 35 years of experience working on vintage motorcycles, with a speciality in Honda SOHC/4 with a focus on the CB750 and other models as well from 1966 - 1985.
______________________________________
1993 HRC RS125 | 1984 NS400R | 1974 Honda CB750/836cc (Calendar Girl) | 1972 CB 500/550 Yoshi Kitted 590cc | 1965 Honda CB450 Black Bomber | 1972 Suzuki T350 | 1973 88cc | Z50/Falcons Pit Bike | 1967 CA100| 1974 CB350 (400F motor)...and more.
______________________________________
See our latest build 'Captain Marvel' CLICK HERE

 

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