1965 Bridgestone Sport 90 Engine Seized

[stingray68]

I just picked up my first Bridgestone.  It is in decent shape over all, but the engine is seized.  I bought it from the original owner that purchased it back in 1965.  He told me that he used to go out and kick it over once a month or so, but a few years ago had heart surgery and that’s when it locked up.  I removed the top end and from what I can tell the piston and bore are in good shape.  I have been soaking it in miracle oil for about 3 weeks and still nothing.  Does anyone have any suggestions as to how to determine what is seized?  I don’t want to rebuild the entire engine, but will if I have too.  Thank you very much for any advice or information you can share.  Thank you all in advance.  Mike

[Mopar392]

Hi Mike,
First try and remove the cylinder, if you are able to do that then its another issue. If the cylinder will not slide off the piston you may opt to try some of other members witches brews to get it free. If that doesn't work then a mallet and block of wood be be required to break the piston loose. That being said, be careful not whack it too hard so that the rod does not bottom out on the crank or you will ruin the rod bearing.
Good Luck,
DL

[slawsonb]

If it comes to the tapping (beating to death) phase, I usually split the cases so the bottom end is free to drop down as the piston moves. I am not a 90 guy, so not sure exactly how to implement this strategy, but it is useful if the crank bearings are what is causing the lock-up. Start with the cylinder removal step as DL suggests.
...bert

[dcr]

If you have to go the way of blunt force, take precautions to eliminate (as much as possible) the impact forces being absorbed by the rod and crank.

[slawsonb]

dcr, this is exactly why I split the cases (on a twin) so the crank, rods, bearings do not get the loading from driving the piston out. On a twin, you can put the top case edges on 2x4's to allow the crank to drop as the piston moves down.
...bert

[mqtsteve]

The small single cylinder bikes have a right/left crankcase not top/bottom.  I don't think splitting the case will work on the 90/100.  Steve

[oldbikeguy]

Hi... saw your seized engine post & thought I'd chip in a thought or two.... It's been my experience with 2-stroke engines that if you can't remove the cylinder after the head has been removed, then the seize is most likely, the rings to the cylinder wall...
I have had EXCELLENT success with using a penetrant called "KROIL"... I retired from a Dept. of the Navy job where I was a mechanical inspector who inspected thousands of complex shipboard pieces of machinery & when something was "seized" the best penetrant the mechanics used was KROIL...
That said, many auto parts stores sell KROIL in pint cans and larger.... I've also seen it for sale direct online from the mfgr ( Tennessee, I think)  With the head removed, apply a couple of tablespoons of KROIL on top of the piston & let it soak over night, then try turning the engine by putting an oil-filter strap wrench on the flywheel, & try turning in both directions.   
I restore vintage 60s-70s motorcycles ( mostly Japanese-Bridgestone) & have 25 cycles that I have had good success with KROIL.
One last thing... on your bike... try putting shifter into neutral position & see if sprocket will turn freely.. if it does, then your tranny is probably OK.
Dale in Washington State

[disc_valve]

Hi, Foljks,

OdBikeGuy's suggestion  sounds a good one, but there is one word of warning about using a strap wrench to turn the mag flywheel om a seized engine. Depending on the direction of turning, you will be either pulling the piston down or pushing it back up the bore. If you turn it in the "push" direction, the con rod will be under compression (rather than tension) and too much "oomph" on the strap wrench could bend the rod.

Don't ask how I know this, but to be safe unbolt the cylinder so that it is free to slide up the studs. Then if the rod tries to push on the piston , the cylinder will move rather than bending the rod. You should be able to apply as much pressure as you like (within reason) in the other direction.

With luck, though, a soak in the magic juice will do the trick for you.

Graham




 

[stingray68]

Thank you all for your help and suggestions.  I have tried a few of these ideas and will give it another shot this week.  The cylinder looks so clean I just find it hard to believe that the piston is stuck, but I did remove the cylinder nuts and was NOT able to pull the cylinder up off the studs "like the piston is stuck"  Anyhow, I am going to try to use the strap idea with the nuts off to see if I can push it up the studs.  Keep the ideas coming and I'll keep you all posted.  I too have used Kroil and have always had outstanding results.  This one however has proved difficult, thats the reason I find it hard to believe the piston is stuck.  Thanks again to all and I'll keep you posted.....Thank you, Mike

[slawsonb]

You will need to make sure the sealant between the base of the cylinder and crank case is broken loose. This can sometimes be accomplished by tapping the sides of the cylinder with a rubber mallet (be careful not to hit the fins with a glancing blow or with anything harder than a rubber mallet or you can break or crack the fins. If tapping does not work, you may need to work your way around the cylinder base with a thin chisel to crack the sealant. Again, go easy and work your way around.
 
It's corrosion between the ring and piston that locks it up. As this corrosion grows down in there it tightens the ring against the cylinder. This is caused by galvanic corrosion between dissimilar metals, aluminum (piston) and iron (ring). (We all hate this when it seizes an engine, but these metal selections are perfect for use in an operating engine.)

...bert

[stingray68]

Hey Bert,

   That is where I am at now....That sealant is proving to be very strong still after 50 years.  I will give the chisel a try tonight.  Thank you again and I am learning alot with this project and one of the biggest lessons is patience!!  I'll keep posting my progress....Thank you, Mike

[stingray68]

I was just thinking about the sealant around the cylinder.  I have ordered a replacement gasket, but is there sealant along with the gasket and if so what do you all recommend.  Thank you, Mike

[slawsonb]

Mike, sealant does not come with the gasket, but take a look at this thread for some recommendations.

http://bridgestonemotorcycleparts.com/index.php?topic=1703.0

Go easy with the chisel and the thinner it is the better to avoid damaging the case or cylinder. Also don't drive it too deep as the cylinder skirt extends into the case when assembled.

...bert

[OldSwartout]

Most sealant will soften at 250°-300°F, not enough to hurt any of the hard parts, or even most rubber parts. A torch or heat gun will help.

[stingray68]

Good Morning Everyone!! 

   I have been working on the disassembly of this Bridgestone Trail 90 engine for on and off now for few months and I was wondering if anyone had any ideas for removing the piston pin so I can remove the piston from the connecting rod. Also, what is the best practice for removing the connecting rod from the rotary valve.  Thank you very much to all. Mike

[mqtsteve]

Hey Mike,
Have you looked at the manuals download section?  They are very helpful!  Here's a link:
http://bridgestonemotorcycleparts.com/index.php?action=downloads;cat=1
Both the parts manual and service manual are available.  There are a couple of small spring clips one at each end of the pin.  They can be removed with a pair of needle-nose pliers.  Then the pin can be pushed out with a socket or a bolt whatever fits.  I'm not sure what you mean about removing the connecting rod from the disc valve?  They aren't directly connected?  I hope this helps, Steve

[dcr]

I suspect you are looking to remove the connecting rod from the crank to replace the crank bearing? If that is the case, you will need to find a shop that rebuilds cranks as these are pressed together (with great force I might add) and this job is best left to the experts. A fairly large hydraulic press is needed to separate the pieces and then the reassembly process must be done to exact tolerances.

Dan

[stingray68]

Thank you both for the advise.  Steve...I did see in the manual the parts and did remove the retainer clips.  I will select a proper socket to push the pin through. Also, Dan is right on the money....I would like to replace the crank bearing.  I would prefer to send this out as recommend....Anyone know of a shop located in Southern Wisconsin/Northern Illinois?  Otherwise, I can ship....Thank you all again for your help.....Best Regards, Mike

[mqtsteve]

Millennium Technologies in Plymoth,Wisconsin does all kinds of engine services including crank building and cylinder repair/re-plating.  Several members have used there services and were satisfied.  Here's a link: http://www.millennium-tech.net/serviceInfo.php?id=4
I had mine done locally but checked with Millennium.  A single cylinder crank rebuild was around $90-$100 if I remember right.  Good luck, Steve

[stingray68]

Hey Guys,  Another question for you all.  I have the LH side of the crankcase and the crankshaft is really stuck.  I don't see anything in the manual about having to have this pressed out.  I want to replace the crankshaft bearing in the crankcase housing. Anyone have any tips?  Thank you all again!! Mike