J-red, too much compression

[DEG305]

I just got a new piston from baileys for my J-red 670 and after installing it the saw has so much compression that the only way to start it is to clamp it in a vise then use two hands with a very firm grip. So far I've managed to break the starter rope and after replacing that I pulled the rope and nut thru the starter handle ruining the handle. Will a jug from a 266xp with a decom fit the 670 ?

 

[WKEND LUMBERJAK]

Does the saw turn over easy with the plug out?

 

[pioneerguy600]

I just got a new piston from baileys for my J-red 670 and after installing it the saw has so much compression that the only way to start it is to clamp it in a vise then use two hands with a very firm grip. So far I've managed to break the starter rope and after replacing that I pulled the rope and nut thru the starter handle ruining the handle. Will a jug from a 266xp with a decom fit the 670 ?

What is your squish measurement? Sounds like your piston might be hitting the top of the cylinder or very little clearance between the two. No way there should be that much compression.
Pioneerguy600

 

[tlandrum]

that saw would never have that much compression without there being a serious problem. i can pull over a saw with 200psi with no decomp like its nothin. like has been mentioned you may have clearence issues. better check it over before you totally reck it.

 

[Scooterbum]

Sounds like it's time for some thick base gaskets.Check the squish.

 

[DEG305]

Yes, the motor turns over real easy with the plug removed. and altho I didn't measure the squish the new piston was the same as the old one in all respects, except for the scoreing

 

[WKEND LUMBERJAK]

were the head gaskets the same?

 

[tlandrum]

unless you mic everything on that piston to make sure crown is same height and pin location is the same there is no guarentee that the squish is the same .... check the squish...

 

[Cantdog]

What is your squish measurement? Sounds like your piston might be hitting the top of the cylinder or very little clearance between the two. No way there should be that much compression.
Pioneerguy600

+1 No way that much comp is right. Has it actually started it this way??
How much oil did you use on reassembly?? To much oil can cause this kind of resistance. Is the piston size code correct for your cyl?? (A,B,C etc.) These are just my first thoughts but that much resistance is not normal, something is amiss!!

 

[MathuisMaximus]

Is the spark plug hitting the piston?

 

[4000fixed]

J-Red compression

Had some of these saws come in the shop years ago. The guys almost couldn't pull them. We installed 2 cylinder gaskets, and never had a come back.

 

[DEG305]

Well after some time to think about the problem, I figured out what was wrong with the 670. I had replaced the flywheel with one that I "thought" was the same as the one that was on it but after removing it and compairing it to the original I found that it was off timing by about 10 to 15 degrees causing the engine to fire prematurly causing it to detonate early. Put the correct flywheel back on and it runs ok. BUT, no one answered the original question that I asked, Will a cylinder from a Husky 266XP, 268XP with a decompression valve fit the J-red 670?

 

[Cantdog]

Well I've never seen a 266 or 268XP with a decomp (not that that means they didn't make one) The short answer to the question is yes either of those cyls will fit the Jonsered 670, however the isolation block, carb, air horn and choke pull will have to migrate with the cyl as well. The impulse setup and choke/high idle systems are very different between the two.