Crank width reduction

[Motoplas]

Hi All,
I am in the process of removing the generator and starter motor from my Gsx1100. the motor will be used for Road racing in a Motoplas frame and I want to do away with the cover.
Should the oil holes in the crank be welded up to prevent oil flow?
I will be shortening the crank and replacing the cover with a flat plate.
Any one any ideas?
Regards,
Noel

 

[triffecpa]

Noel - I've got a GS1000 roadracer that has had the alternator removed. The prior owner did the work though. It looks like a 1/4" aluminum plate was made for the left side of the engine (I assume that they used the stock cover for a pattern). There's a small round addition to the middle of the plate to cover the end of the crank. It's all welded up so be oil tight. Can't imagine that they actually shortened the crank. I can send a pic if you're interested in looking at it. Tracy

 

[robinjo]

I don't think the crank needs to be shortened once the alternator and starter gear are removed, only the flat plate and a cover for the starter hole are needed. Or do you want to cut the crank to lighten it?

p.s. What is a Motoplas frame? Very curious about that one...

 

[lecroy]

I had an APE cover that I gave away last summer. It seems that the crank (83my) extended out the cover. I think the seal was made to the crank and not the starter nut. There are no oil holes in the cranks I have used. They have all been solid.

 

[Motoplas]

The Motoplas was built originally for Laverda's in the late 70's for use as racing bikes.They then changed from twin shocks to cantilever and added Kawasaki and Suzuki engines and used the frames in Endurance racing, the frame was designed by an Italian engineer the plastics by Motoplas.
The frames kits were then sold in Aus in limited numbers for donor engines.
The running gear is all top quality, gold line brembo's, PVL wheels,Marzocchi forks, Bitubo rear shock.

 

[Guest]

The seal rides the crank. I guess you could run it without the nut.
http://gszone.biz/starterplates.html

Tell our phone guys that I said they could buy one without the nut.

Jay

 

[lecroy]

Jay, that third bearing support looks alot like mine from RC.

 

[Guest]

The one RC used to make didn't have the support bearing out on the end of the crank like ours.

Jay

 

[rosco15]

How do you plan to start i if you cut the end of the crank off? And if you road racing, don't you need the charging system?

 

[triffecpa]

you run a "total loss" ignition system. Essentially all the power to run the ignition comes from the battery. You simply recharge the battery after each race or practice session. For starting, there are two options. First is to simply push start it, second is to use a set of starter rollers (you use your rear truck wheel to turn the rollers and then use the rollers to turn the rear bike wheel and bump start it without having to push it). It's not really htat hard to push start one of these bikes. Actually it's easier than on a big twin. The advantages are two fold. First is weight reduction. You get to lose the starter and alternater and starter gears and several electrical components. Secondly the engine no longer has to spin the heavy alternator on the end of the crank and will rev faster.

 

[lecroy]

I got some nice marks on my arms this summer from playing starter boy. I did not know that anyone still used rollers to start a bike after the 70's.

 

[triffecpa]

"I got some nice marks on my arms this summer from playing starter boy. I did not know that anyone still used rollers to start a bike after the 70's."


Go to an AHRMA national race. They're all over the place. Some of the big singles and twins are virtually impossible to push start by hand. And what kind of marks does one get being a "starter boy" anyway?

 

[rosco15]

Not a great pic, but you can see the plate with the end of the crank sticking out. There is a nut on the end that you use a hand held car starter to get the bike running. It's used on big CC high compression motors. If your not holding onto the starter tight it can wack you. That is an 8.60 small tire bike.

 

[rosco15]

Or try this vid. first is a pro-stock. second is the bike above.
http://media.putfile.com/dragbike-outboard-starting

 

[lecroy]

"I got some nice marks on my arms this summer from playing starter boy. I did not know that anyone still used rollers to start a bike after the 70's."


Go to an AHRMA national race. They're all over the place. Some of the big singles and twins are virtually impossible to push start by hand. And what kind of marks does one get being a "starter boy" anyway?

I would never had guess it.

The bikes are 1600cc T/G class. Normally I don't have any problems, but once in a while you get the compression just right and the starter has enough force to twist my arms. Normally it's when your not ready for it to lock and then you get hit with the starter arms.

 

[triffecpa]

Sounds like some of the confusion over starting methods here is coming from the Drag Racers vs the Road Racers. I haven't seen any roadracer types using the hand held external starter method, but a lot of them use starter rollers or push start. Interesting that the technology is available to both, but things have gravitated down differnet roads. I know that I get my arm cocked every now and then with my 18v cordless drill. Can't imagine how much torgue a 12v auto starter must have. Yikes.

 

[Guest]

Maybe because the drag motors that use those starters have compression ratios from 13 to 1 to 17 to 1. You won't find that in too many road racers.

Jay

 

[triffecpa]

"Maybe because the drag motors that use those starters have compression ratios from 13 to 1 to 17 to 1. You won't find that in too many road racers. " Jay

Not for more than a couple of laps anyway...