DIY or Not DIY?

[skiri251]

Next installment of my BS (BridgeStone .. LOL) 200 motorcycle rebuild saga.

Finally I got all the parts necessary for crank rebuild.

I also found a local shop who can do the rebuild. The cost would be $300~.

If I can do it myself with this cheapo 12ton HF press in a link below, I will save $200 and have a press in my garage for future use (or it will get in a way just collecting dust.. LOL)

https://www.harborfreight.com/12-ton-a-frame-industrial-heavy-duty-floor-shop-press-1667.html

Should I do it myself or ask the pro?

I understand that alignment is very important when the crank gets reassmbled. But I can't image making some sort of jig will be that difficult. I was kind of surprised that a lot of shops declined to do the job saying they don't have a jig for it.

Here's the crank.

There are holes in those circular disks (what are they called?). They line up so I can use them for truing?

 

[slabghost]

Well whenever I'm faced with the question of buy tool or pay someone. Unless tool costs more by a good margin I buy the tool. If I only use it once afterward I still feel it was a good deal. Now on assembly of the crank. It looks to me like it may be possible to get parts together too tight. I'd try assembly with some shim material and remove the shim stock after assembly. Check tolerances and tighten where needed.

 

[skiri251]

Thanks.

What do I need to disassemble/assemble the crank?
I image some sort of steel plates or angles which go in between disks so I can push the crank pin out. Then as you say some sort of distance pieces to adjust the tightness for assembly. Do I need any sophisticated measurement tools other than calipers, micrometers, and feeler gauges?

 

[joedrum]

hmmm cant help here but for sure seek someone with some experienc e and jig and willing if nothing more that to talk to someone who got a clue ...like you did already...id be temped to use the guy and watch like a hawk to learn sometimes this beats tool buy ..as you see smart hands ...the bs build is a rare one ...so dont gamble to much ..im sure there is not many in the country ...a well built bridstone will be quite the show stopper where ever it goes .....get the motor right skirri ..the entire game is won and lost here

 

[skiri251]

Actually the local guy I found needs to ship out the crank to another shop (sounded like they do twin snowmobile engines, that's way they have a jig). So I don't think I can watch.

I am not sure BS200 is that valuable. I am not aiming for consourse restoration either. The only thing I can think of other than dimensional alignment would be dynamic balance. But then again, I don't think this shop would dynamically balance the crank for $300..

At this point, I am tempting to do it myself....
I saw a few threads on BS forums so maybe I should consult them.

 

[dan filipi]

Have you tried breaking down that crank assembly yet? Is it all pressed together?

 

[slabghost]

I expect it is just pressed together. Before attempting disassembly I'd use a straight edge and put a permanent mark on lining up all the pieces. It looks like just the outside disks need removed. So you'll need a jig made to support just those disks. Press will push the shaft through. We have a few machinists on here that will probably check in with more specific instructions.

 

[skiri251]

I was browsing BS forums.

Yes, the crank parts are just pressed in. No splines, no alignment marks.
The shop manual doesn't show crank dimensions so I should really measure and write down before I start disassembly.
They also recommended to scribe alignment marks before disassembly as slabghost suggested.

I want to take apart center disks to replace an oil seal. Center bearing feels really solid but oil seal is old and hardened. It is not a NOS oil seal though. I just picked up Taiwanese one with the same OD/ID. Width is a bit smaller. But better than old stock oil seal I think?

That means I need 180 degree crank pin alignment jig. I found a few photos of DIY jig on BS forum.

Wow, this is getting interesting!

 

[skiri251]

Oh and this is the fully disassembled crank (NOT MINE, got it from BS forum).

 

[dan filipi]

Fun stuff!

 

[slabghost]

Getting very interesting. You've done everything else yourself. My money is on you getting it right.

 

[skiri251]

Thanks! :hihihi:

First I need to buy the press. HF has A frame and H frame. Which is better? H frame costs a bit more.

 

[dan filipi]

Interesting crank design, I expected to see a single shaft thru the center with everything pressed onto it.

 

[slabghost]

The bigger the press the more uses you'll find for it. I bought the H frame. It's still in the boxes at the moment. Not sure which has what advantage.

 

[skiri251]

I found a review in HF web site that said A is better because it auto-centers the pressing force.
It seems to be avaliable online purchase only but I guess I am not in a hurry..

 

[joedrum]

cool thread ..skirri gomman go just infrom yourself the best you can ...im with v im backing you ..sent out stuff dosnt sound good to me third party stuff ....

 

[skiri251]

Thanks Joe.

I should do it for fun, that means full blown DIY LOL.
It's not that I am going to race this bike (maybe just a little bit..)

 

[sledge]

thats the hard part about rebuilding a multi-cylinder 2 stroke eng. is getting the Crank apart AND Back together , because every Rod and Piston is seperated at the Crank with a Seal. . . because they are just like 2 or 3 , single Cylinder 2 strokes , connected at the Crank . I have Owned 11 GT750 Suzuki's ... and a few GT550's and GT380's also ... they have to go back together , Perfect , or the Crank won't even turn in the Case . but a good Machine Shop should be able to do it . :builder:

 

[skiri251]

sledge » Tue Mar 08, 2016 5:48 pm[/url]":2sq7q3e9]
thats the hard part about rebuilding a multi-cylinder 2 stroke eng. is getting the Crank apart AND Back together , because every Rod and Piston is seperated at the Crank with a Seal. . . because they are just like 2 or 3 , single Cylinder 2 strokes , connected at the Crank . I have Owned 11 GT750 Suzuki's ... and a few GT550's and GT380's also ... they have to go back together , Perfect , or the Crank won't even turn in the Case . but a good Machine Shop should be able to do it . :builder:

This means the distance between two rods must be very accurate?
What about the lateral play of the rods?

 

[joedrum]

yep this is deal skirri ..sledge nailed it with some fine words and probably the best we have in the 2 stroke field here with all his experience with them ....