GS 610cc

[Guest]

Eyup

Has anyone had a 610 cc set up on a 1978 550?
I was wanting to know a good stating point for Jet sizes?????
any help would be appreciated,
Thanks from rainy Yorkshire

[GregT]

Eyup, lad, thee should look through thy collection of Performance Bike mags. They did a big 550 back in the day and some of the info may be of use.

What carbs are you using ?

[gsru]

Now then Mr T
I'v still got some old BSH but not any Performance mags, ya ony keep em 30 year or so Then ya get rid Then ya need em, Heyho!
Im using the 78 slide carbs can't remember the number off hand VM wotsitmebobs !
I'l have to wait n see if anyone comes up with any sizes,
cheers Ru

[Chuck78]

I just refurbished one last year with 20,000 miles total (not sure how many miles on the Wiseco 610 kit) that sat garaged for 21 years. I believe it had somewhere around 102.5 mains if I recall. Possibly 105? It ran well, I wanted to do plug chops, but it was not my bike and I was in a hurry to get the guy out the door on his new machine. Needles were raised one notch, so 1 clip position lower. Pilot jets were stock size. K&N pods, Kerker performance baffle and 4-1

If you ever wear out those bores, DynoMan Performance sells custom order 630cc pistons for gs550's. I believe JE Pistons may manufacture them.

[Chuck78]

FYI this was with stock VM22's. Stock cams.
Clutch would not hold under hard use, performance springs had to be swapped. Not much power off the line due to small displacement, but once the R's were up, it was a blast, and much easier to lay into turns than a 750/1000 due to weight.

[gsru]

Cheers Chuck
That's just wot I needed to know!
I had no real idea where to start So
I'l start right there! I intend to get it set up on the
dyno But I need it up and running first,
Thanks again,
Ps I used to have a PE400 F&%?ing mental and always been One I WISH I had'nt let go, Heyho
Keep Smilling

[Chuck78]

I'm second-guessing myself now, maybe that bike had 110 mains in it? Start high, you can always go lower, tune with an air fuel ratio gauge and wideband O2 sensor on the dyno, or plug chops on the open road, or wideband O2 and AFR gauge if you have that luxury. It's really awesome to have that setup. A Dyno is even better!

[Chuck78]

I sure wish that I would have started cataloging every engine set-up I've wrenched on in the past 8 years since moving from old cars/trucks to primarily vintage japanese motorcycles for 8 years heavily...
Details including cranking compression ratios, and then noting what jetting & carb settings I had arrived at, how it ran, and air fuel ratio or plug chop readings... I've had so many different setups on my bikes and friends / "customers," a lot of it gets a little muddy in my head trying to recall exact details of bikes with subtle differences...

[GregT]

I sure wish that I would have started cataloging every engine set-up I've wrenched on in the past 8 years since moving from old cars/trucks to primarily vintage japanese motorcycles for 8 years heavily...
Details including cranking compression ratios, and then noting what jetting & carb settings I had arrived at, how it ran, and air fuel ratio or plug chop readings... I've had so many different setups on my bikes and friends / "customers," a lot of it gets a little muddy in my head trying to recall exact details of bikes with subtle differences...

I've got around 30 years worth of hard covered exercise books - the workshop notebooks. I've told my wife to hold an auction when I'm gone - and enough people know about them she says she's had bids already...