1985 GS700ES -- Big Bore Kit, or equivalent power increase

[mthomason]

I am looking to getting some more power out of my GS700. I think the route to a larger displacement would be preferred. So far I have already put the bike on a weight diet, next are more modern lighter wheels. The weight is now at 460lbs wet. Already a Yosh race header and Dynojet kit with pods...I want more from this bike.

Does anybody have any advice?

[christopher_2]

GS1000 motor, do a search here you will find a few posts on the change. Sounds like it is pretty easy and would be a 300cc displacement increase.

[Billy Ricks]

I am looking to getting some more power out of my GS700. I think the route to a larger displacement would be preferred. So far I have already put the bike on a weight diet, next are more modern lighter wheels. The weight is now at 460lbs wet. Already a Yosh race header and Dynojet kit with pods...I want more from this bike.

Does anybody have any advice?

RS flatslides wake them up nicely. A 750 crank and rods with the 700 pistons will get you that 50cc back and bump compression up to about 10.25:1.

[mthomason]

Thanks!

Thanks, for your replies... 50cc gain is not too much, I think maybe a 5-10 hp gain at most from now. But, it is more! Either way, new engine (GS1000) or 50cc sounds like allot of work. Sounds like fun, too! One of these bikes with about 100-105 hp would be real nice.... BR: what pipe/silencer, and rear sets do you have on your machine (nice, by the way).

[Billy Ricks]

Thanks, for your replies... 50cc gain is not too much, I think maybe a 5-10 hp gain at most from now. But, it is more! Either way, new engine (GS1000) or 50cc sounds like allot of work. Sounds like fun, too! One of these bikes with about 100-105 hp would be real nice.... BR: what pipe/silencer, and rear sets do you have on your machine (nice, by the way).

The exhaust is a stainless Yosh Duplex meant for a '92 GSXR 750. The can is a Yosh RS-3 carbon and the rearsets are from a mid '90s GSXR. Thanks for the compliment.

BTW, if you can get your hands on a Wiseco 814 kit and use the 750 rods and crank you'll get more hp. The RS flatslides really wake these bikes up. 34mm is what you should use if you can find some.

[mthomason]

1100 Engine?

BR: Thanks, for the reply info.. I, too, though the 814cc kit might be the way. Any idea if a GS1150 engine might fit, or even an oil-cooled GSXR1100? I really don't want a heavier 8 valve engine from a 70's era bike...

[kingofvenus]

There is a past bike of the month winner that was a oil cooled motor conversion, a picture of it is in the past "BOM" gallery. (jan '04)

[mthomason]

Now that's what I'm talking about! 1100cc of GSXR (Katana, really) type power in a nice GS package. Wow! He had to raise the take 3", and I am sure there must have been a few other obstacles. This ceratinly sounds intriguing. Thanks,for the reference!

[oldschoolGS]

An excellent 750cc recipe,

816cc big bore kit
.325-.330 lift cams w/slotted sprockets and aftermarket springs
Dyna or Accell ignition
flatslide 34mm carbs w/pods
race 4-1 pipe

You will have a totally different bike with a ton of upper midrange and a serious kick at 7500 rpms. For a 3 year period my '83 was built as described above (but at 802cc), the bike was very well balanced and would out run a mostly stock 900cc-1000cc bike of the mid 80's. She would lighten the front wheel at 7500rpm in 3rd gear and easily overpower the rear 140 tire.

It will take a few mods to really pump up a 750 of this era, but a properly modified 750 can achieve a very nice balance between power/weight.




Ride On, Ed.
2005 GSF1200SZ
1983 GS750ED
1992 Ducati 900SS