GS1000 bigger valves

[Guest]

Have a spare mill (1979 GS1000) that I plan on hot-rodding.

First question regards the valves. What are the downsides to having APE install larger valves?

The tentative plan is to bore +3, run cams etc. I have RS 34mm and RS 36mm carb banks in my stash already.

Engine goes into a Harris F1 frame.

All mods must be pump gas compatible.

Any other build guidelines would be welcome-thanks!

Already have welded basket and e-ignition and 42mm carb boots/rubbers (to mate RS carb banks).

[Nessism]

A welded crank would be good insurance.

I can't think of any disadvantage with oversize valves other than cost. One of the bikes I bought and fixed up had oversized intake valves and that seemed like a really nice head.

[slayer61]

More importantly, hannibal, where in gods name did you get a Harris frame??

[Big T]

If you go too far with the cams, you have to convert to shim under bucket

+1 on the welded crank

[hannibal smith]

More importantly, hannibal, where in gods name did you get a Harris frame??

They are still making them as far as I know...........I hope! I was just going to order one, and build the mill while I wait for it to ship.

[80GS1000]

Have a spare mill (1979 GS1000) that I plan on hot-rodding.

First question regards the valves. What are the downsides to having APE install larger valves?

The tentative plan is to bore +3, run cams etc. I have RS 34mm and RS 36mm carb banks in my stash already.

Engine goes into a Harris F1 frame.

All mods must be pump gas compatible.

Any other build guidelines would be welcome-thanks!

Already have welded basket and e-ignition and 42mm carb boots/rubbers (to mate RS carb banks).

I have a similar config (Wiseco 1100 cc big bore/Web .395 lift cams/RS34s) in my built GS1000 engine. We'll need pics of that Harris frame once you get it.

Based on my experience, suggest a secondary breather on the clutch cover venting to a baffled catch can to relieve the excess crankcase pressure created by the big bore/high compression piston kit to prevent blown out gaskets/seals.

What pipe will you be running?

[GregT]

Cost is the downside. Having APE do it ensures good valves - in my experience there are some poor quality stainless valves around.
Yes, a welded crank is good insurance if you're planning on racing it - or going over 9000rpm.
Our race engine uses the stock breather - a good bore job with well seated rings won't have blowby.

The biggest decision is valve shims. Over or under. Over limits valve lift to a safe .415inch. Big HP needs more lift than that.
Valve springs are another point. Good springs with around 90lb on the seat and shims under will allow 10 grand plus with a welded crank

[steve murdoch]

They are still making them as far as I know...........I hope! I was just going to order one, and build the mill while I wait for it to ship.

https://www.harris-performance.com/product/harris-frame-kit-f1/

Heading to the lotto shop.
Twin shock, Hannibal?

[hannibal smith]

What pipe will you be running?

4 into 1 stainless.

I already have an "over carbed" bike, and even the RS 34mm seem big. The XR69 ran 29mm if I recall. What was your reasoning for running the 34 vs. the 36?

[hannibal smith]

https://www.harris-performance.com/p...-frame-kit-f1/

Heading to the lotto shop.
Twin shock, Hannibal?

I am probably going to go with the mono. The best way is to get the frame, swingarm, and tank in one order I am thinking. It's expensive, but it's not over priced IMO.

[hannibal smith]

Cost is the downside. Having APE do it ensures good valves - in my experience there are some poor quality stainless valves around.
Yes, a welded crank is good insurance if you're planning on racing it - or going over 9000rpm.
Our race engine uses the stock breather - a good bore job with well seated rings won't have blowby.

The biggest decision is valve shims. Over or under. Over limits valve lift to a safe .415inch. Big HP needs more lift than that.
Valve springs are another point. Good springs with around 90lb on the seat and shims under will allow 10 grand plus with a welded crank

I am going to run over. My lift will not exceed 0.400, so I am going to keep that element as factory. I am running a 2 valve from 1979, so I have no illusions in comparison to a new bike. It's probably going to scratch 160+ anyway. It should weigh sub 400 pounds without any problem.

[80GS1000]

4 into 1 stainless.

I already have an "over carbed" bike, and even the RS 34mm seem big. The XR69 ran 29mm if I recall. What was your reasoning for running the 34 vs. the 36?

My GS1000 doesn't see any track duty so I wanted more streetable torque and a wider powerband. The 1980 model of the GS1000 came stock with the larger 34mm CV carbs so it made sense to keep the inlet velocity high and run the 34s vs. running a larger carb which may make more peak power but lose throttle response and torque at lower RPMs.

With an earlier GS1000 you may want to run a smaller carb since the 34s might be too big for your application.

Is this engine going in a street bike, roadrace bike, drag bike...?

[GregT]

4 into 1 stainless.

I already have an "over carbed" bike, and even the RS 34mm seem big. The XR69 ran 29mm if I recall. What was your reasoning for running the 34 vs. the 36?

I've built and run big GS1000's on 29's and Keihin CR 31's and 33's. The 31's are great for a streetbike. The RS34's will be usable only because of the accelerator pumps. 29's do limit top end slightly.
An early head properly ported will give very good midrange as the ports are smaller meaning higher gas speed.
We've used both early heads and the late 1100 head - both with big valves - on our racebike. Peak HP not a lot different - but midrange was miles better with the small-port head.
I won't go to CR35's. For our circuits here, the small gain at top end isn't worth the midrange losses.
On 100 octane with CR33's it makes around 130HP at the wheel - with a flat torque curve.

[hannibal smith]

I've built and run big GS1000's on 29's and Keihin CR 31's and 33's. The 31's are great for a streetbike. The RS34's will be usable only because of the accelerator pumps. 29's do limit top end slightly.
An early head properly ported will give very good midrange as the ports are smaller meaning higher gas speed.
We've used both early heads and the late 1100 head - both with big valves - on our racebike. Peak HP not a lot different - but midrange was miles better with the small-port head.
I won't go to CR35's. For our circuits here, the small gain at top end isn't worth the midrange losses.
On 100 octane with CR33's it makes around 130HP at the wheel - with a flat torque curve.

Thanks! Definitely confirms my suspicions on carb size.

First thing will be to get the crank welded. What are good sources for this service?

[GregT]

Thanks! Definitely confirms my suspicions on carb size.

First thing will be to get the crank welded. What are good sources for this service?

Search rapidray's answers on this. For work within the US he has the answers.