XR 600R - cutting out a mid upper range

Just finished putting my bike back together and it runs great at idle to 1/4 throttle, but any more and it sputters and cuts out. Before putting it back together I did not change or adjust anything and before making repairs it ran fine. Any ideas?

Sounds like the float level needs to be set correctly (14mm)

I have a QS carb if that helps. It worked fine before I took the motor apart and I did not change anything when I put it back together. At first I thought that the jetting may be off, so I adjusted the jetting 4-5 click rich and that did not help so I went in the opposite direction by 4-5 clicks and same thing - no difference. Think the float in the carb might be stuck??

It could be stuck or just got knocked out of its float level setting.

OK, it is not the carb. Installed a known good carb and same issue. So I started troubleshooting the electrical components. It appears that there are two issues, the ignition coil and the alternator exciter coil. The ignition coil reading between the plug wire and the secondary coil should fall between 7.4 - 11 K ohms but read 3.0 K ohms. The alternator exciter coil should fall between 230-320 ohms but read 88 ohms.

Since I have an XL alternator I thought I would install that first to see if it helps. The problem I am having now is the leads on the XL are different than on the XR. Does anyone know which wires on the XL tap into which wires on the R?

Don't know for sure. You should only need the one exciter coil connection to get the bike to run. If it's not black with red like the XR, use your ohmmeter to find the coil with a few hundred ohms. The lighting coil is only like one ohm so it should be easy to tell the two apart.

Jon,

Check your Air cleaner.

If its clogged up, it will sometimes give you the same symptoms.

OK, getting a little frustrated with this bike. I installed the XL alternator and same thing - cuts out at mid to upper rpms. To more accurately describe the problem, it sounds like it is hitting the rev limiter.

Here is what I have done so far that has not cured the problem:

1) swapped with a good carb

2) changed out the alt to XL alt that ohms out good

3) changed out spark plug boot

4) removed air filter

5) opened up exhaust (thought this might be clogged but it was not)

6) checked coil and it is good. At first I thought it was bad because the reading was low, but in a separate manual that I have it gives a lower value if you check it without the boot. I was checking it without the boot and it falls within parameters.

The only electrical changes I have not made so far are to replace the spark plug and/or change out the CDI. I would think in both cases if they were bad then there would be no spark and the bike would not run at all.

The only work I did to the bike before I had this problem was replace the piston rings and install new valves and valve guides. Would it be possible that during assembly I did not install the cam correctly and that it is mistimed? Would the bike even run if the cam was off by a tooth? Anything else I may have not thought of?

OK, here it is November, and I finally got it running!!

here is how it went:

I eventually replaced all electrical components and had the same issue so it had to be mechanical. I ran across a used XR head for ~$35 so I picked it up figuring I could use it in my troubleshooting process since it was inexpensive. The head had two vavles that leaked and of course the valve seals also leaked (common) but I figure I would run it as is. I installed it and the bike runs good, which is impressive considering the condition of the valves to begin with. I don’t know if i originally installed something incorrectly or if the timing was off (did not seem like it) but it works now. I figure I will run it for awhile and enjoy it before taking it apart again.

thought I would update in case someone else has a similar problem....

have fun:ride:

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