• Husqvarna Motorcycles Made In Sweden - About 1988 and older

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76 250 WR Cylinder/Stroke Issue

O

Oldmanshred

Husqvarna
AA Class
I bought a rolling 76 250 WR frame along with an engine and parts. The engine # says it would be a match to the 75 250 WR, but when turned the crank I heard a thunk. When I took the head off and cranked it the piston emerged over the top deck enough that the ring on the piston was fully exposed?? The piston fits the bore perfectly claiming to be 2nd over. I do notice it has one ring, while another mind 70's CR250 engine I have has a very similar piston but it is double ring. So my question is:
Do I have a frankenstein with wrong size rod?
Do I have the wrong piston?
Do I have the wrong cylinder?
The image is at what would be top dead center, you can see how far it protrudes.
This is what came with it under the claim it was a complete engine but clearly would have never been able to run.
 

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Measure from cylinder top to the top of piston at BDC. Add the distance it sticks out and see what the stroke is. At bdc is the top of the piston level with the bottom of the exhaust port? What does piston measure?
 
auto said:
Measure from cylinder top to the top of piston at BDC. Add the distance it sticks out and see what the stroke is. At bdc is the top of the piston level with the bottom of the exhaust port? What does piston measure?
Click to expand...
When I get the stroke length, where do I go next? I will measure it this a.m. and post it.
 
Here's a picture showing the piston at BDC. It clearly doesn't come to the bottom of the exhaust port. So, the rod is too long for this cylinder? Or cylinder is too short for this rod? Lol. Not laughing really as this is a mess.
 

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Oldmanshred said:
Here's a picture showing the piston at BDC. It clearly doesn't come to the bottom of the exhaust port. So, the rod is too long for this cylinder? Or cylinder is too short for this rod? Lol. Not laughing really as this is a mess.
Click to expand...


Looking at the pictures it looks like the piston top is about the same distance above the exhaust port at the bottom of the stroke as it is above the cylinder at TDC. So maybe the stroke is correct but it has the wrong piston. If you can, try to measure the stroke with a set of calipers. If needed raise the cylinder up with some spacers so you have a the top of the cylinder edge to measure from.

Marty
 
When you look through the intake with reed block off and piston at BDC do you see two boost port windows in the piston? If no,wild guess someone put a early short rod piston in your motor. But that piston would only have a single boost port window in it. If that's the case you just have to get the correct piston,easy fix
 
Odd thing is that piston looks used. I would think that if someone went to the trouble to replace the rod, they would put in a new piston. Everybody I know that replaces the rod does a complete bottom end. It is possible that they messed up and put in the wrong rod and just gave up. My gut feeling is the rod is stock and they had a piston and just put it in to sell it. Do what Auto said and measure stroke the way he suggested. I have a 75 WR and it has been great.
 
You either have a long rod or a tall piston. I'll take pics of my 1973 problem in the morning. Kinda weird prob in 1975? All the parts that you mention were bought as a setup for a roller. I think you got a pile and with work you will figure it out! It could be anything from crank to rod to piston to cylinder. Lets start with the numbers! And Pics!! A side shot of the cylinder, a clear shot of the piston head with any identifeing numbers and the crank out of the case with the piston and all the associated numbers, rod center to center piston wrist pin to crown, stroke of piston and rod in cylinder. Let us Know!! Going back to the post 1 That thing is hanging out big time!! This is a lot of problems. That is gonna hafta come apart no matter what!! Unless we can prove it's the cylinder! Chris
 
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