Two Stroke Crank Build

[LC Racer]

Not really a project, but I generally build a few of these over the year. Yamaha TZR250 2MA crankshaft, built to racing spec with flat cage big end bearings and Koyo TZ spec main bearings. The rods are TZ spec too but the parts are the same for the road bike these days.

I find it quite theraputic to be honest, I was lucky to be taught by one of the best two stroke tuners in the business, apart from a hydraulic press and various measuring equipment it does involve the use of a large copper mallett, which is always a bonus!

I aim for zero run out at the crank ends but it takes a fair amount of persuasion and time to get there sometimes . . . . . . . .

 

[brightspark]

do u get them ballanced once built up

 

[dobbslc]

That's what the mallet is for!

 

[roofman]

has the bearing on the taper end run hot anytime...looks blued up

 

[Wallace]

Not done a crank rebuild and true for years, my Father taught me on my C15T and used oversized rollers to save replacing the crank pin!

 

[Robotstar5]

....I find it quite theraputic to be honest, I was lucky to be taught by one of the best two stroke tuners in the business, apart from a hydraulic press and various measuring equipment it does involve the use of a large copper mallett, which is always a bonus!....

Stan Stephens?

 

[AndyStobbs]

Just stripped a rotax 947 and need a complete crankshaft overhaul on that. Could do with my press built up. Never done a crankshaft but would like to try.

 

[LC Racer]

has the bearing on the taper end run hot anytime...looks blued up

No it's brand new, must be just a trick of the light. The outer bearings take a right hammering in a race bike, I've never actually had one go but i always change all the bearings at rebuild time

Stan Stephens?

No Uncle Bob

Just stripped a rotax 947 and need a complete crankshaft overhaul on that. Could do with my press built up. Never done a crankshaft but would like to try.

I've done a few different twins and singles but I only do the TZR's these days, there is without a doubt a knack to getting them right but it just takes practice really. I wouldn't want to do a triple though, you'd need a proper indexing jig for that to get the crank web timing right. Mark the webs and and measure everything before you strip it and inspect everything very carefully. It's condensation that causes the most damage to the crank pins, if there is any signs of pitting they need changing.

The mallet is to 'adjust' the run out. Dial gauges, v blocks and a vintage surface plate do the rest

Just in case anybody wonders what a 2MA is:

 

[lotus_esprit_s1]

I once had two rd500's and five spare engines when the engines could be picked up for £150 each back in late 90's when no-one was interested in two strokes. wish I still had them would be worth a tidy sum!

 

[daleyd]

In my fantasy garage would be one of the Japanese market reverse cylinder models, or possibly one of the later SP models - I loved those bikes!

 

[dobbslc]

I raced one a few years ago in the yamaha past masters club. It made about 55 bhp at the wheel and was the most unlucky bike I ever owned!
Massive highside at Lydden, got taken out at Oulton Park, that was a complete write off, and taken out again on the slow down lap of practice at Brands Hatch!
I flogged it after that

 

[normspanners]

Bloody modern stuff, disc brakes and all----------these are the ones with 70 ish mm front spokes, I used to work on when 16.

 

[LC Racer]

I raced one a few years ago in the yamaha past masters club. It made about 55 bhp at the wheel and was the most unlucky bike I ever owned!
Massive highside at Lydden, got taken out at Oulton Park, that was a complete write off, and taken out again on the slow down lap of practice at Brands Hatch!
I flogged it after that

That's a YPM bike, it's all still going strong! Might have raced against you Dobbslc if it wasn't too long ago?

 

[roofman]

In my fantasy garage would be one of the Japanese market reverse cylinder models, or possibly one of the later SP models - I loved those bikes!

yea with the full 70bhp race kit...nice

 

[daleyd]

yea with the full 70bhp race kit...nice

Still looks awesome 25 years later....

 

[dobbslc]

That's a YPM bike, it's all still going strong! Might have raced against you Dobbslc if it wasn't too long ago?

It was about 11 years ago, I made a return to racing after racing 250 singles and a Yamaha FZR 400, I only got to 3 meetings and had the above "incidents", I remember Neil Ronketti helping me out, I have a news letter somewhere from the YPM stating that was the highest highside he'd ever seen and I won un-luckiest man of the meeting award too!
That bike was jinxed!
I sold it to a lad called .......Wright l can't remember his first name, he went very well on it. ( I did sort it out properly first)
I still have the FZR and do the very occasional trackday now.
Happy days!

 

[LC Racer]

It was about 11 years ago, I made a return to racing after racing 250 singles and a Yamaha FZR 400, I only got to 3 meetings and had the above "incidents", I remember Neil Ronketti helping me out, I have a news letter somewhere from the YPM stating that was the highest highside he'd ever seen and I won un-luckiest man of the meeting award too!
That bike was jinxed!
I sold it to a lad called .......Wright l can't remember his first name, he went very well on it. ( I did sort it out properly first)
I still have the FZR and do the very occasional trackday now.
Happy days!

Ah a bit before my time then, I didn't start until 2007. Dan Wright has over the years done very well on your bike, won a fair few and been on the podium a load of times, races other bikes but still has the TZR. How much of the original bike is left though who only knows!

 

[dobbslc]

Triggers broom after the Oulton Park one....
A list of the damage :
Frame, both pipes, rear wheel buckled, front tyre = 5" flat spot, front brake master cylinder, all bodywork, tank, bars, clocks ( I still have what's left of the tacho for sentimental reasons) leathers and lid.
The little **** that tagged me never even came to see if I was alright!
I "walked away".
It's good to know it's still going strong and Dan is doing well.

 

[ronan]

Bloody modern stuff, disc brakes and all----------these are the ones with 70 ish mm front spokes, I used to work on when 16.

I want that front drum brake for my special.