78 750 to 850cc Vintage Street / Track theme build

[one_civic]

And here's the end result, There is a small gap in the right hand lower corner, this is most likely from my excessive / frustrating removal of the lower base gasket with my razor and die grinder, I'm pretty confident the lower Cometic base gasket will take up this clearance, and maybe a little bit of Honda Bond as well for precaution.

 

[one_civic]

Onto the head now, The head is an 83 850cc with the intake ports being roughly 34mm but the intake manifold rubber's being roughly 32mm. I am not an expert on 850's with CV carbs and the year's they used them but I'm guessing the extra 2mm on the head is for the O-ring's and manifold boot to seal. I will be using carbs from a 86-87 Canadian GSXR 750, They are referred to as Mikuni VM 29ss flatslides, not to be confused with early performance Mikuni VM 29 round slides,

More on the carbs for later,

Right now here are some pics of the re-surfaced head, my head had a high spot in the middle of the timing chain tunnel, my machinist had to mill 0.020" off the head, He advised me to check Piston to Valve Clearance with the engine assembled using a head and base gasket, My guess for the high spot is sometime in this 850 engine's life, it developed a small oil leak around the head and the previous owner re-torqued the 4 outer oil channel head bolts causing it to warp, but who know's

I had previously lapped in the valves and done some quick porting of the exhaust ports. As you can see I am not professional at porting and plan to clean them up a bit with some light 600 grit sandpaper, but that's good enough for me for now.

 

[one_civic]

Quick valve lap with fine compound, Yeah I know the valve's are placed on the wrong side, :fatigue:

 

[one_civic]

As you can see, not professionally done, I did not touch the intake side as I am no expert in porting and did not want to screw up the intake flow, my reasoning behind the exhaust side was to help it flow a little bit more.

If some member's have Constructive criticism to help me smooth out the exhaust ports, That would be awesome!

 

[one_civic]

Got my new re-spaced carb linkage back from my machinist for my VM29ss GSXR carbs, Everything lined up perfectly, money well spent

some measurement's of the 850 head, intake manifold boots, and carb throat, their actually 33mm but the inside neck is 29mm,
If I wanted too down the road, they could be bored out to 33mm.

 

[one_civic]

 

[one_civic]

I know I'm going to have some weird flow problems, 29mm inner carb neck size up to 33mm outer carb neck, back down to 32mm intake manifold boot, then to 34mm cylinder head, I may port the intake manifold boots, but I don't know yet?

Any advice from the pro's on here for what to do?

Here they are on the bike mocked up, lot's of clearance from the tank and getting my modified manual cam chain tensioner back from my machinist soon.

 

[Chuck78]

Great thread, great bike, great direction you're taking it!
We're those carbs only available on Canadian models???? I think I recall seeing a set of those recently on another bike. Very nice looking. What other work did you have to do to re-space them? Mount to the 750's vm26 rack?

Nice job on the Koni's as well, do you by chance have more Koni literature from wherever you got that spring chart from? I found a great rebuild manual for them, but unfortunately I want paying enough attention in high school french class, so I can't read them well! Lots of great photos though, step by step. From a Moto Guzzi website I believe I got the download from.

My Koni 76F's have red straight rate springs that just have a dark red dot on each. I'm looking further for other remnants of paint dots when I get off work.

 

[one_civic]

Unfortunately that's all the info I've found for the Koni's and from talking to Robert Hagg AKA [FONT=wf_segoe-ui_normal] Konimon / Koniking on ebay. Again for anyone looking for seals / info etc. This is the guy to go to, he is very passionate about vintage dirtbikes and loves rebuilding, talking to people about their bikes suspension setup.

His email is,

rhaagusa@yahoo.com


[/FONT]

 

[one_civic]

As far as the carbs Chuck, these were only available on the slabside 85-87 GSXR 750's in Canada and everywhere else in the world except you guys in the US, (emission reasons possibly?)

I mounted these carbs on the 850 head that came with the 83 850cc engine which has 34mm intake ports and roughly 32mm intake manifolds, some people have told me that the 34mm head only came on gs1000's?

Again I am not sure what you guys got compared to the rest of the world, the 2 inner carbs line up perfectly while the 2 outer's have to be moved, My machinist also moved the throttle linkage to the middle instead of between carbs 3-4 giving me more clearance for the stock center push / pull throttle cables / linkage. He also drilled and tapped a hole for me to use both accelerator pump's from my second set of parts carbs.

Agemax should come along soon with some more info about these carbs. He and Robert Barr put together an O-ring rebuild kit for these carbs. I will try and take some more pics and basic measurement's as far as carb spacing between the stock Vm29ss GSXR Slabside layout and the re-spaced ones my machinist did.

Again, I do not recommend to try and re-space carb rack linkages yourself unless you are a qualified machinist. Without proper professional machinst tools / taps / vernier calipers' etc, it is very easy to screw up the spacing.

I'll post some more pics of the carbs / spacing within the next couple days as well as the rear sets and brackets I will fabricate.

 

[Gs1000g]

As far as the carbs Chuck, these were only available on the slabside 85-87 GSXR 750's in Canada and everywhere else in the world except you guys in the US, (emission reasons possibly?)

I mounted these carbs on the 850 head that came with the 83 850cc engine which has 34mm intake ports and roughly 32mm intake manifolds, some people have told me that the 34mm head only came on gs1000's?

Again I am not sure what you guys got compared to the rest of the world, the 2 inner carbs line up perfectly while the 2 outer's have to be moved, My machinist also moved the throttle linkage to the middle instead of between carbs 3-4 giving me more clearance for the stock center push / pull throttle cables / linkage. He also drilled and tapped a hole for me to use both accelerator pump's from my second set of parts carbs.

Agemax should come along soon with some more info about these carbs. He and Robert Barr put together an O-ring rebuild kit for these carbs. I will try and take some more pics and basic measurement's as far as carb spacing between the stock Vm29ss GSXR Slabside layout and the re-spaced ones my machinist did.

Again, I do not recommend to try and re-space carb rack linkages yourself unless you are a qualified machinist. Without proper professional machinst tools / taps / calipers' etc, it is very easy to screw up the spacing.

I'll post some more pics of the carbs / spacing within the next couple days as well as the rear sets and brackets I will fabricate.

Hey man great build, can I ask why you just didn't go with the 850 carbs or even 1000cc carbs if you need increased fuel demands and jet accordingly?

 

[Chuck78]

Hey man great build, can I ask why you just didn't go with the 850 carbs or even 1000cc carbs if you need increased fuel demands and jet accordingly?

I assume for the same reasons Suzuki didn't continue to use BS32 carbs in the mid to late 1980's, flatslides are better for performance.
I don't believe those are smoothbores, but they appear to be direct linkage non-CV flatsludes, which isn't the most common setup to find here in the US. non-CV's are best for all out performance but require a well versed rider's appropriate throttle input to keep the velocity and engine e response in it's peak efficiemcy/power sweet spot. CV carbs have butterfly valves that restrict the middle of the venturi, and then a airflow sensitive spring loaded slide that moves up on its own based on airflow velocity and pressure differential. With the manual slide carbs, the venturi is unobstructed and the rider is left to have 100% control of slide position.

When whacking throttle wide open on a CV, you open the butterflies fully, but they are still blocking through throat in the middle, and the slide is left to open at its own rate based on airflow, air port size and engine vacuum, and spring tension. On a direct linkage carb, you can open the throttle and monitor engine sound and power output and optimize it yourself. Too much opening of the directly attached carb slide will kill your velocity and lead to poor performance until the engine catches up or you back off to its sweet spot.
More user input required but with that the ultimate performance can be gained. Constant engine feedback and rider wrist input is required though.

 

[one_civic]

I assume for the same reasons Suzuki didn't continue to use BS32 carbs in the mid to late 1980's, flats lies are better for performance.
I don't believe those are smoothbores, but they appear to be direct linkage non-CV flatsludes, which isn't the most common setup to find here in the US. non-CV's are best for all out performance but require a well versed rider's appropriate throttle input to keep the velocity and engine e response in it's peak efficiemcy/power sweet spot. CV carbs have butterfly valves that restrict the middle of the venturi, and then a airflow sensitive spring loaded slide that moves up on its own based on airflow velocity and pressure differential. With the manual slide carbs, the venturi is unobstructed and the rider is left to have 100% control of slide position.

When whacking throttle wide open on a CV, you open the butterflies fully, but they are still blocking through throat in the middle, and the slide is left to open at its own rate based on airflow, air port size and engine vacuum, and spring tension. On a direct linkage carb, you can open the throttle and monitor engine sound and power output and optimize it yourself. Too much opening of the directly attached carb slide will kill your velocity and lead to poor performance until the engine catches up or you back off to its sweet spot.
More user input required but with that the ultimate performance can be gained. Constant engine feedback and rider wrist input is required though.

Couldn't have said it any better Chuck, their easier to tune with pods as opposed to CV as well.

 

[limeex2]

The creativity and skills by the members here never ceases to amaze me. This is a great build and documentation. Thanks.

 

[one_civic]

bought some R1 rear sets, $100 Canadian

 

[one_civic]

 

[one_civic]

Quick mock up with zip ties,I'll have them mounted before the end of the week,

Going to make sure that I can still use the kickstarter

 

[one_civic]

Rear sets done, will have to get a shorter female shift rod in the future but for now their perfect, cutting down my seat foam and getting it re-done to help ergonomics

 

[one_civic]

I needed a manual cam chain tensioner and the only one available is around $140 can. through SPS. So, I decided to fabricate my own with the help of my machinist, here are some pics, It is basically a ground down automatic tensioner with a 7/16 fine threaded rod with a silver soldered nut machined down exactly identical to the OEM one,
It also has an E5 female Torx stud tapped / locktited and peened over at the end of the threaded rod for adjustment and carb clearance. I could not find a bolt long enough / threaded all the way to the end and my machinist did not recommend to tap one .

 

[one_civic]