Looking for xj650 mechanic help in Virginia

Hi there I’m John, new to the forums and I am here looking for some mechanical help in Virginia. I recently purchased a 1980 xj650 Maxim not running from the previous owner. He rebuilt the carburetors, replaced the battery, and coils. I installed a new set of plugs and got it running. I had the carbs synched, float levels set and jetted for the 4 to 1 pipe. It now runs but will not run correctly after 2500 rpm. I have tried many things to try and improve the problem but haven’t managed to fix it. I would be willing to pay a mechanic in or within 200 miles of Virginia to help me get it sorted out. The bike also only has 4000 Miles.

 

Is your bike using the factory airbox? Or is it running pod filters?

 

My bike thankfully still has the stock air box

 

You need the valve clearances checked first. Then a compression test. Then check if the plugs are getting fouled. Since it runs you have sparks at the plugs so you probably have a carburettor issue. Do you have a Haynes manual for your bike? How much maintenance have you done on bikes before? You could always get the carburettors rebuild, one of our members rebuilds carburettors and all you would have to do is sychronise them when you get them back.

 

Okay, I just hadn’t checked my valve clearances as I was told it wasn’t necessary until I reached 5000 miles. I have worked on many four cylinder motorcycles and I’m a full time auto mechanic but this motorcycle has me mind boggled. I had the carburetors rebuilt once and I synchronized them as well with no change in the issue.

 

Yes you are right at that low mileage. What are your mixture screws set at?

 

The first valve clearance check / adjustment is at 3000 miles, and then every 5000 miles thereafter. Most of the valve clearance "wear" occurs during the first 8-10K miles of engine use, as the valve closure (under spring force) pounds the somewhat soft valve seat deeper and deeper into the cylinder head, causing the valve clearance to shrink (a very bad thing........). After about 10K miles, the valve seats have been pounded in sufficiently to the point where seat recession is no longer an issue, and just normal wear-and-tear adjustments are necessary.

 

They are set at 2.5 as per the manual, I also tried 1 3/4, 1.5, 2, and 2 1/4 with the issue still there. Idles all day long, you take off and it chugs a bit then clears up from 1500-4500 and begins to break up like the choke is on and then if I hold it wide open it will keep doing it and very slowly start to clear out then it will hit 8 and rev to 9 and then you shift and it does the exact situation again.

 

I will check the valve clearances as well now that you say it’s at 3000 I’ll check them over real well.