GS1100 - Straight Cut Gears: Nice to Have or Required?

[quexpress]

Hi!

It has been mentioned and explained more than a few times that at a certain point, the GS1100 helical gears (on crank and clutch basket) may cause problems (i.e.: break something).

It was added that the solution for this was to use straight cut gears.

I can easily understand the need for these on drag bikes, race bikes, etc. However when is there a need for these straight cut gears on a street bike? Where does it change from "nice to have" to "must have". Is it at a particular horsepower level? If so, what is that level?

Thanks!

[TheCafeKid]

Are you racing it? It is true that the helical gears, when beating on your bike on a regular basis will stress the clutch basket due to side loading. If you romp on em and hammer thru gears enough without attending to the issue, eventually the backing plate on the basket will give up the ghost and blow itself apart. The result of this is not only expensive but could be catastrophic not only for the bike, but for you ass well. It could blow holes in the cases, destroy the crank etc etc. But, unless you have deep pockets the cheapest and second mos effective fix for this is simply pulling your clutch basket and having a heavy duty backing plate installed. These are much stronger and the pins are welded. It's alot less likely to fail. Going to straight cuts is not only expensive as the crank has to be pressed apart to replace the helical gear and and the drive gear on the clutch basket must be changed as well but it requires splitting the cases obviously to remove the crank. If you're doing that you might as well have it trued and welded as well. You're looking at close to a grand probably said and done with shipping. Just doing the HD basket will run you around $350ish plus some down time unless you have a spare basket.

[Nessism]

Don't let blowerbike scare you. If you ride your bike hard get your clutch hub rebuilt as Josh says and relax.

[TheCafeKid]

Don't let blowerbike scare you. If you ride your bike hard get your clutch hub rebuilt as Josh says and relax.

Well now, dont misconstrue what im sayin either. If you RACE it, you'd probably be wise to listen to the pros and go with the SC gears. Otherwise, the basket rebuild is probably more than enough for a street duty racer Keep in mind also SC gears will be much noisier than Helical. If you've ever ridden a 77-79 GS750 (which came stock with straight cuts) you'll know what Im talking about. The first time I rode one, it felt just like home coming off of Kwackers But, before I realized and learned they had them stock, I was actually concerned my tranny might be suffering because they do whine quite a bit.

[quexpress]

Thanks guys!

A clarification is required I guess. No I don't plan on racing it, and will most probably not hammer it between each gear.... well not often.

I asked this question to "educate myself" on the need for these straight cut gears.

I keep wondering "when are these required".

[rapidray]

My recommendation would be that anything you are putting a slick & wheelie bars on, straight cut gears are a MUST!!! Also, anything with a big street tire over 150 hp I would straight cut. That's just ME though & I build everything overkill to make it as unbreakable as possible. Ray.

[blowerbike]

Don't let blowerbike scare you. If you ride your bike hard get your clutch hub rebuilt as Josh says and relax.

hahaha,
i don't preach straight cut primary gears silly girl.
i preach HD backing plate kits.

[quexpress]

My recommendation would be that anything you are putting a slick & wheelie bars on, straight cut gears are a MUST!!! Also, anything with a big street tire over 150 hp I would straight cut. That's just ME though & I build everything overkill to make it as unbreakable as possible. Ray.

Thanks Ray!
That's exactly the kind of info that I was looking for!
Normand

[Big Jay]

One way to tell if you need straight cut gears, is to remove the clutch basket assembly and see if the gear has been hitting the crank cheek. With big power, the helical gear will suck the clutch gear into the crank cheek. and you can see the marks.

Otherwise, all you need is this;

http://gszone.biz/clutches.html

[quexpress]

One way to tell if you need straight cut gears, is to remove the clutch basket assembly and see if the gear has been hitting the crank cheek. With big power, the helical gear will suck the clutch gear into the crank cheek. and you can see the marks.

Otherwise, all you need is this;




http://gszone.biz/clutches.html

Great insight! Thanks!
Normand

[blowerbike]

ive seen stock engines load the basket primary gear into the crank throw before.
stock engines that was ran very hard that is.
i ran my 1168 turbo w/ helical gears..maybe 220 HP + or -....
never side loaded into the crank but i did break the weld on 2 rivets on my basket once..found it under normal weekly inspections.
went to (free)750 straight cuts the next season.
bad choice for a turbo..bad choice for sliders to.
i now have (not free)1100 ratio straight cuts.
you can get by with helical gears making a decent amount of HP if your running a slider clutch.
i'll throw this out there...
if your running 8's in the quarter..get straight cut primary gears installed and forget about it.
one less thing to worry about.

[jimb12]

How hard do you ride the bike and what kind of work has been done to it?

I have seen an 1166 streetbike break a welded helical clutch basket drag racing. It had a stock rear wheel with a Dunlop K591 on it, stock swingarm and no wheelie bar. Little surprising with that skinny tire but it happened.

[blowerbike]

How hard do you ride the bike and what kind of work has been done to it?

I have seen an 1166 streetbike break a welded helical clutch basket drag racing. It had a stock rear wheel with a Dunlop K591 on it, stock swingarm and no wheelie bar. Little surprising with that skinny tire but it happened.

maybe a bad weld or assembly job.
that is not the norm for sure.