Opinion on gs crank w/ turbo

[Guest]

I've got a GS1100et with an old school Blake turbo set up. Cycle did a story on this particular bike back in 1981. Everthing in the motor was stock then, now It's got a 1260 kit and billet basket. Ignition is a Koenig belt driven mag and a Karata lock up clutch hat. Crank is unwelded.
I've got it apart to weld the crank, but am thinking I should have the gears changed to a strait cut drive. I know I'll have to change the clutch basket to match. My deal is this is a street bike... nothing more. Should I do the gear or is it a waste of time and money?

[LarryT]

I sure most will tell you to go with the straight cut gear but i ran a car tire turbo(GS1000) drag bike for 10 years ran 5.29 @130 mph 1/8 mile 1.17 60' with the helical gears no problems. Id save my money

[chiphead]

If I remember correctly, you'll get more horse power with straight cut gears but you get noticeably more gear whine from them. Street bike? Save your dollars and use it to buy beer to drink in your garage/basement shortly after you scare yourself with that turbo.

[madjack57754]

I bought this bike from Blake right before the magazine came out in 81. I've put 7500 boosted miles on it with limiting the waste gate to 15 pounds It'll make your eyes get large mostly because of it overpowers the stock chassis. My Busa is quicker, faster, smoother, but is nowhere near as fun to ride as the GS. Ran it at Bandimere in a fastest streetbike shootout and only ran 12.28 but MPH was 168. Laid a black track to the 1000ft mark

[49er]

I bought this bike from Blake right before the magazine came out in 81. I've put 7500 boosted miles on it with limiting the waste gate to 15 pounds It'll make your eyes get large mostly because of it overpowers the stock chassis. My Busa is quicker, faster, smoother, but is nowhere near as fun to ride as the GS. Ran it at Bandimere in a fastest streetbike shootout and only ran 12.28 but MPH was 168. Laid a black track to the 1000ft mark

Sounds like you've given the bottom end a good workout over a prolonged period. Why have you suddenly decided to weld the crank? Are you splitting it to replace the bearings?
Your ET could have been improved considerably by limiting your boost to around 10psi. Mind you, your trap speed wouldn't have been as impressive.
If you go with straight cut gears it will whine.

[rosco15]

A couple of the guys on there have already had problems with the angle gears. You already know angle gears are a weak point. Why go thru all that time and money and not take care of it.

[LarryT]

What problems have they had ?

[madjack57754]

I tore it down because the cam chain broke. It bent 7 valves, broke 3 rockers, screwed up the guides, broke the cast guide pocket that the chain guide sits in. Heres the worst part.....It wasn't running when all this damage occurred.
Long story short... the clutch started slipping, so I tipped it on it's side using a tiedown from the handle bars to the garage rafters to lean it way over. I pulled the clutch cover, adjusted the lockup and put it back together. I pushed the starter button and all I got was a click. Being the rocket scientist that I am, I figured tipping it had caused something to come adrift. Everything had power except the starter wouldn't spin. Living on a real big hill I coasted it down and let the clutch out. All the broken parts are the result. The autopsy reveled that there was a cam sprocket bolt wedged between the sprocket for the cam on the crank and the care bottom. In 27 years the cases have never been apart, all four of the sprocket bolts are still in the proper place. What I figure happened is during assembly in Nippon one of the gnomes got fat fingered and dropped a bolt down the tower. It must have dropped off to one side and lodged there. When I tipped the bike way over like I did, the lost bold found it's way into the cam chain.... Bing bang boom..... blown up motor while not running and thats why I split the cases

[lecroy]

Running teens in the 60' is getting down there. I wouldn't test my luck. But that's not what your doing and I tend to believe your most likely safe with the stock gears (if they are checked to be ok).

Back in the day I ran my 1100 with a Mr. Turbo kit on the street for years. 7 PSI boost on pump gas. Ran well and could spin the tire at a twist. A lot of fun. Crank was stock also. So was the clutch. Those were the 80's.....

However I would NEVER just have a 20+ year old crank welded, EVER. To me this is the waste.

Sorry to hear of the damage. I won't lecture you on your methods. I have made some very brilliant choices as well and learned from them.

R U from the Black Hills?

[rosco15]

The helical gear causes the clutch gear to get sucked into the crank cheek. I've seen pics of the gear broken right off the basket. Most guys that dragrace change to the straight cut gear because of this. At 168 mph in the 1/4 he is making alot of HP.

[Hap Call]

The helical gear causes the clutch gear to get sucked into the crank cheek. I've seen pics of the gear broken right off the basket. Most guys that dragrace change to the straight cut gear because of this. At 168 mph in the 1/4 he is making alot of HP.

Yep, it's the axial thrust that the helical gears place on the basket that cause the problems. If you have the crank apart, go ahead and have the straight gear put in. As far as having the unwelded crank, you've been lucky - see bikes with a lot less HP with twisted cranks.

Peace of mind - it's worth it.

Hap

[LarryT]

im guessing the reason i got by with the helical gears was the chromoly backing plate and the steel Kawasaki KZ clutch basket.this might be helping the gear from twisting.I still see no need with a street tire.

[madjack57754]

I know know my bump start choice was not the best idea. I've had larger brain farts but this was a first. I've never heard of anyone else blowing up a motor that wasn't running except for IEDs
lecroy yes I'm west of Deadwood, out by the Wyoming state line

[lecroy]

lecroy yes I'm west of Deadwood, out by the Wyoming state line

My father was born and rasied in the Black Hills area. He passed away when I was a young man. He got me into motorcycles against my mother's wishes. I have been working on the restoration for a about 4 years now and am going to dedicate it to him. I will post some pictures of it soon. Maybe you will enjoy them, being from the area.

In my own experience and people I know who actually build and race that they are right about the welding, and cracked gears to a certain extent. I had asked Pearson about the gears at one time and he basically said the 9's was about the limit that they would run them. But he knew of guys running SC (8.90 index) with them. But I have to agree with Mr T. on this one. You can get away with so much on a little street tire.

I have said this before, it's the initial hit (of the force from a launch) that kills the parts. Launching a 10" car tire bike is way different than a bike with 1" of contact surface, on the road.

I think Jake's bike is a good example of just how much abuse the stock cranks and clutches can take. I know your out there, what 60's were you running towards the end of last year? I bet you were in the 20s as well.

[madjack57754]

I appreciate the thoughts and advice. I was going to send the crank to PMFR/Ward, but changed my mind. I'm ordering falicons complete super crank with the heavy duty rods
That bike has always been my favorite of the many and no sense cheaping out now. It doesn't see a lot of ride time but it's my ultimate stress relief when work and customers really start to get me down