Tuning Guys/ Piston Guys/ Help this Man!!

[Guest]

Ill get to it,

OOOOk, Bought a gs750 engine off of craigslist (40 Bucks and an old Xbox =D), with the initial plans the swap out the 750 Cylinders, pistons, and wrist pins from this Parts Bike I have (GS850). I opened up the 850, not too bad inside. Then Came the 750, Holy ****... It had been Bored to 850CC, the Cylinders look BRAND NEW and it had these Pistons Inside of it... POP.Y is the marking on the Piston. Is that uhh, POP Yoshimura?? Or what are these exactly. Need help Identifying these Pistons please!




On to second matter at hand. To finish this build, I need some info from you guys. Comparing the two heads, The 850's Intake Port and Exhaust Ports are much wider than the 750's. AND it looks like the entire valvetrain from the 750 will swap over entirely to the 850 casing. I only have a set of Mikuni BS34 CV Carbs and have rebuilt them, painted them, and hear theyre a good improvement over the Stock GS750 Smoothbore Carbs. Can I switch the Head from the 850 with the 750 Valvetrain and BS34's onto this High Comp Bored Out 844CC/750cc Motor.

- Will this (after polished Ports) Help with ANY performance upgrades by flowing (theoretically) more air.

- Are the BS34's better than the Stock GS750 Carbs for Street Use Only?

- Is it a better option the keep the 750 Head with the 750 Valvetrain in this scenario and buy a set of used gs750 carbs?

- Can I run, Tune, Keep Efficiency AND Power with this 850 Head/750 Valvetrain/BS34 Carb setup...


If you have any idea what Im talking about please share any info you have. If you are a guy who knows a guy who knew a guy, I want that Guys Number. If you own a Shop or have ever been around a shop that Tunes these GS bikes, Ill take their numbers too!!

BTW I have 850 Cylinders, Pistons & Pins EXTRA, send a PM we can trade around.

THANKS THANKS THANKS

-Sean

[7981GS]

I used '80 850 cylinder head and '80 GS1000 34CV carbs on my first '79 750/'80 850 conversion.
Worked like a champ!
To answer your question, YES! Do it.

BTW, those pistons are more than 11:1 comp. ratio.
You might want to use an '80-up 1000 cylinder head with a larger combustion chamber volume to lower the comp. ratio for street use.
Check to see if the cylinders need to be notched for valve clearance.
Or, just sell me those pistons.

Daniel

[rapidray]

Sean, call me at 714--356-7845. I just built one with those same pistons. Yes, they are Yoshimura pistons. Ray.

[Sci85]

Wow, what a find. You're one lucky bug!

[seanspecht]

7981GS - With this sort of setup, will the BS34's feed enough atomized fuel into the cylinders?? Im sure I'll be investing in a dynojet kit when this thing gets closer to completion, but I have seen warning about HP ranges and carbs that will choke the higher RPM range into a leaner mixture?? Mikuni has some of this information in the pdq's online. Any thoughts?

RapidRay - I really appreciate your time! I wrote down the advice and conditions we spoke about, but still have a few more questions. Mainly about finding TDC and cam timing. Most manuals only speak of how to remove cams etc. I'll be putting it together as soon as my gasket kit arrives from Japan. I'll post some glam shots of the final build.

Sci85 - I think your right! In all seriousness though, I will only be running these pistons for a season or two just because THIS project is the one and only 80's Suzuki GS I'll build... There will be another Suzuki, probably the 90's era GSXR, but when I finish my fun around town with this bike, the stock 850 pistons will replace the Yoshimura POP set, and the Yoshimuras will be thoroughly cleaned, mounted on a rod/crank display and have a glass cube around it. No pistons will be damaged in this build

[7981GS]

7981GS - With this sort of setup, will the BS34's feed enough atomized fuel into the cylinders??
Im sure I'll be investing in a dynojet kit when this thing gets closer to completion, but I have seen warning about
HP ranges and carbs that will choke the higher RPM range into a leaner mixture?? Mikuni has some of this information in the pdq's online. Any thoughts?

They are large enough to use on the GS1100G's and the 4-valve 1100E's.
Both of those models come stock with the same size carbs.
I am using a set of 34's on my '82 GS1200G also with no problems.

Daniel

[seanspecht]

7981GS - Superb. Good info, I appreciate it!