Jonsered 630 Idle and RPM Issues

[VI Guy]

The Jonsered 630 I recently picked up is having issues with idle, and with RPM when operating on its side. I know this has been covered numerous times in the past, but thought I would run it by you guys for opinions from past experience.

When I first got the saw, it fired right up and seemed to run good but a bit smoky. I tried adjusting the carb, but it was impossible to tune it correctly. At first I figured a carb rebuild would take care of it, but while I had it running I turned it onto its right side (bar side) and the RPM went up. When I flipped it on to its left side (pull start side) it died within a couple of seconds. At that point I put the saw away so I don't cause any damage if she is running lean.

I guess my question is have any of you experienced the high idle on one side and engine dying on its other side? I had an old Husqvarna 50 Rancher that would increase RPM when flipped on either side, but never experienced this. I am guessing it needs new seals and they will probably get replaced regardless. Maybe just a carb issue? I guess I should add that it had about 3/4 of a tank of gas at the time, and other than this the saw seems to be in good shape. It also seems to have good compression (can lift saw by the pull cord without it unwinding).

 

[Kneet]

Most probably an air leak. As you mentioned replace the seals, also replace the o-ring behind the oil pump. Also check gaskets and other intake components for leakage. Put a new kit in the carb. Best is to do a press/vac test to be sure. The amount of fuel in the tank shouldn't be a problem, my 670's only lean out on the last drop of fuel.

It also seems to have good compression (can lift saw by the pull cord without it unwinding).

This is not a very reliable method, because there are a lot of variations in spring tension, weight, friction, etc. Better check the condition of the piston/jug trough the exhaust/intake port, and check if this leak already done some damage, look for scratches and aluminium transfer.

 

[SkippyKtm]

I'm with kneet on this one, probably an air leak. I'm going to post a link to "a poormans guide to vacuum testing" but unfortunately the images are gone ever since AS got hacked, but here goes anyway:
http://www.arboristsite.com/community/threads/poormans-guide-to-vacuum-testing.42768/
It should still be useful, the text is pretty good...

 

[Cantdog]

Yep..... Kneet has given good advise. Depending the age of your 630 it may or may not also have an o-ring on the flywheel side too....same one and must be had from a Husky dealer...not generic o-ring. I'm gonna say chances are pretty good you replace both seals and O-rings and the probable will go away. Other than that and what Kneet already suggested you get to the bottom of it.

 

[VI Guy]

Thanks for the input. I have already ordered the seals for it so hopefully they will be here within a week or two. I took the muffler off and it looks good in there. No sign of scoring or aluminum transfer whatsoever. There was oil and quite a bit of smoke coming out the exhaust when I had it running so I think it was getting enough lubrication.

 

[rickyrooster]

might not be a bad idea to replace the gas line while your at it. There are two different lines sold so make sure you get the right one. Rick!

 

[VI Guy]

I finally got around to rebuilding the carb this evening, and replaced the crank seals and o-rings. It is a night and day difference in how it runs. The carb tuned easily, and it is running great! Judging by the condition of the seals it is no wonder it was having issues. Fortunately the bad seals didn't cause any damage.

I included a pic of the seal from the bar side. It has definitely seen better days...

 

[MarkEagleUSA]

I finally got around to rebuilding the carb this evening, and replaced the crank seals and o-rings. It is a night and day difference in how it runs. The carb tuned easily, and it is running great! Judging by the condition of the seals it is no wonder it was having issues. Fortunately the bad seals didn't cause any damage.

You got lucky. I replaced the oil pump on my 162SE (essentially the same saw as the 630) and the o-ring was bad. Took less than 5 minutes to eat the piston.