Gs1000 Bonneville Bike

[limeex2]

What do the rules state for head work? Specifically 2 ir 4 valves? Big difference. Correct me if I'm wrong, but if there is no written rule against it, its legal. When we roadraced "production" bikes this made for very imaginative and creative ways to go faster

[Agemax]

Gearing will be one of the problems. I have made up an 18T front sprocket for our GS1000 so as to give us a wider range of options for roadracing. Once you have your bike, I'd see what is the biggest front sprocket you can fit and work back from there. With a bigger front, you'll be looking at rear sprockets in available sizes which will fit on a stock cush drive.

I run a 19T front sprocket,48 rear on my GS1000, (530 size) but i have a GSXR 17" rear wheel. I think 19T is the biggest that will fit, i certainly havent seen any bigger ones for sale.

[stevef.]

Gearing will be one of the problems. I have made up an 18T front sprocket for our GS1000 so as to give us a wider range of options for roadracing. Once you have your bike, I'd see what is the biggest front sprocket you can fit and work back from there. With a bigger front, you'll be looking at rear sprockets in available sizes which will fit on a stock cush drive.

Noted, I suppose we will have to see. We do have a good friend who's father is an excellent machinist by trade so he may be able to help with this if need be.

What do the rules state for head work? Specifically 2 ir 4 valves? Big difference. Correct me if I'm wrong, but if there is no written rule against it, its legal. When we roadraced "production" bikes this made for very imaginative and creative ways to go faster

The rules for that engine class say that the engine needs to use the original crank casings, cylinders, and head. Since the 4v design was initially manufactured prior to 81, it's legal. But I do need to start with a bike that originally came with it, which is why I am pretty latched onto the GS1100 at this point.

[RichDesmond]

Gearing will be one of the problems. I have made up an 18T front sprocket for our GS1000 so as to give us a wider range of options for roadracing. Once you have your bike, I'd see what is the biggest front sprocket you can fit and work back from there. With a bigger front, you'll be looking at rear sprockets in available sizes which will fit on a stock cush drive.

Sprocket Specialists will make anything you want as long as it's physically possible.
(Well, they did last time I checked.)

[RichDesmond]

What do the rules state for head work? Specifically 2 ir 4 valves? Big difference. Correct me if I'm wrong, but if there is no written rule against it, its legal. When we roadraced "production" bikes this made for very imaginative and creative ways to go faster

Depends on the sanctioning body. Back when I roadraced, CCS was like that, if it's not prohibited it's allowed. WERA was the opposite, if it wasn't specifically legal, it was illegal.

As always with racers and rulebooks, there will be "creative" interpretations.

[80GS850GBob]

"140mph"
-sounded to me like the guidelines said the engine had to be stock heads, crank and cylinders...{but are internal mods ok?...over bore, added stroke via other oem rods and shorter height aftermarket pistons}
-does the gearing have to be stock offered ratios?...or can you gear stiffer for top end speed?
-if you can't change gearing {much} can you go to taller rims/tires?...or both?
Bonneville is a long run game and average of three passes...as I recall.

[stevef.]

"140mph"
-sounded to me like the guidelines said the engine had to be stock heads, crank and cylinders...{but are internal mods ok?...over bore, added stroke via other oem rods and shorter height aftermarket pistons}
-does the gearing have to be stock offered ratios?...or can you gear stiffer for top end speed?
-if you can't change gearing {much} can you go to taller rims/tires?...or both?
Bonneville is a long run game and average of three passes...as I recall.

"Classic Gasoline- The engines production date shall be prior to 1981. All engines shall retain the O.E.M. heads, cylindeers, and crankcases originally installed at the time of factory production. Above components produced after 1980 and exact reproductions may be legal in Classic class if they offer no competitive advantage. Documentation may be required to prove authenticity of classic OEM standard bore to remain in displacement class. Further increased displacement beyond the class limit shall place the motorcycle in the correct class. GASOLINE ONLY."

This is EXACTLY what the rulebook says. I don't see any mention of the rotating assembly or the valvetrain. Only that the design of the engine MUST have been in manufacture prior to 1981 and externally has to look more or less stock (obviously stated in more specific terms). I would like to avoid having to fight with them to allow an '82 (if they are in fact the same as earlier models) so I am sticking with looking for '80 and '81 models.

Gearing can be changed in any class per the rulebook.

Wheels can be changed in the chassis class which I am looking to compete.

Also, the speed is averaged over the center mile of the course and has to be averaged over two runs. This is done so that you can run both ways which negates any effect that wind could have on the run. So if the wind makes me go 150mph headed east, it could slow me down to 130mph when I head west and we will get the average.

There are different length courses depending on how fast you are able to go. I should theoretically be on the five mile course: two miles to build speed, one timed mile, and two miles to shut down. I could hit the center mile at 138, accelerate to 145 in that time, and my average will be somewhere in between. It's not about top speed, more about showing what type of speed you can maintain.

-Len

[Buffalo Bill]

Looks like you'll only be moved to a higher displacement class if you overbore, however this may put you in the 1000cc class.

[stevef.]

Looks like you'll only be moved to a higher displacement class if you overbore, however this may put you in the 1000cc class.

We're shooting for the 1350cc class. The current record with the AMA is around 130mph. The AMA events are not as competitive as the SCTA events and it appears as though the classic engine designations are also less competitive than the other engine designations. We specifically want to target the low-hanging fruit, so to speak.

[Sam 78 GS750]

This could be interesting. I'll definitely be following along.

[RichDesmond]

"Classic Gasoline- The engines production date shall be prior to 1981...

I read that as 1980 and earlier. 1981 wouldn't qualify unless you can show that they were identical.

[stevef.]

I read that as 1980 and earlier. 1981 wouldn't qualify unless you can show that they were identical.

Good catch!! I am thinking that most, if not all, bikes sold as 1981 model years were produced prior to 1981. But this is something I will be looking at closely on any bike I purchase.

-Len

[850 Combat]

Do you have any place that you can test?

This place is a lot closer than El Mirage or Bonneville

http://www.loringtiming.com/ They can't do real FIA records there, because they only race in one direction, and they doother reasons. A guy went over 300 on a sit down motorcycle there. It is paved. Obviously El Mirage and Bonneville are not. El Mirage is at 2800' elevation. Bonneville is at 4200' elevation. The elevation and the surface both slow down the speeds somewhat compared to what you might find on pavement.

[greg78gs750]

says the head must be oem, but can it be worked?

[GregT]

says the head must be oem, but can it be worked?

I'd read that as the casting must be OEM - but all else is free.