2013 Tc-250r Engine Problems

I have a TC-250R on which the valves stretched and destroyed both cams. I had new valves installed, replaced the cams and timing chain. I shimmed the cams to within tolerances as per the service manual and made sure the cams were in time, using the marks on the cam gears just as the service manual directed. I re-assembled everything, put in some gas and the bike won't start. Checked the plug and coil, and it is getting a spark. I thought it might be a fuel issue then, but I get nothing even using starting fluid. The bike has good compression when it is kicked. Is there anything that I am missing? I was sure I set the TDC valvetrain timing on the compression stroke, but there's always the possibility I did it on the exhaust stroke. Is that even possible? Would that keep the bike from starting?

well, if you did it on the exhaust stroke- the spark would be 180° out (i don't think xlite's spark on the exhaust stroke, but maybe). You also might be a tooth off on the timing chain, but I'd expect an occasional spark-pop. [edit- we talked about this a couple of years ago. I think JonXX or R_Little said it was a wasted-spark system]

sounds like the valves haven't hit anything so you're probably damage-free so far. Are you getting more than one spark? Is the capacitor connected?

you might do a quick compression test to make sure you don't have damaged rings or the ADC is always on. you can ignore the fuel injection system until you get a pop or two with starting fluid.

your tests (feel for compression, spark, starting fluid) were the right way to go- so I'm a little mystified.

I'm going to check it again tomorrow, thanks for your ideas.

Yes, i believe it is a wasted spark.

I never worried about which stroke and never had a problem putting it back together. It always started.

Is the bike kicking back at all?

Check the woodruff key on the flywheel?

We tried the bike again today. Removed the cams, and set the piston to TDC. Then we installed the cams, exactly as the shop manual described. Made sure the ADC is working. Reassembled everything else and tried to start the bike but got nothing. No pop at all. The bike seems to have good compression, and we made sure we were getting a spark at the plug. I sprayed starting fluid into the intake while my son was kicking, and we still get nothing. What should we get if we do a compression test? I'm not sure of the spec for that. I'm not sure what you mean by the bike kicking back.

kicking back: piston coming up on the compression stroke... spark plug fires (perhaps early or there is not enough momentum to make it over TDC) and the piston is forced back down before it gets over the top (IOW: turns the crank backward).

if my theory on sheared keys is right, you shouldn't have a problem with a TC250 because it does not have a worm drive starter.

did you check for multiple sparks- meaning more than 1 per kick? this is feeling like a spark problem.

compression: >100psi (guessing) with the ADC working, but it should start with anything above 80-90. really you're supposed to disable the ADC and see like 175psi.

I would suggest actually testing the compression. Newer four strokes tend to feel like they have good compression even with the plug out with the valve train forces and large magnets in the flywheel to power fuel injection, etc.

I don't think it's a kickback problem. We will check the compression next. I'm guessing since you mentioned multiple sparks, we should be seeing that, not just one spark per kick? I held the plug in the coil while my son kicked and we did get a spark but now that I think about it, it did seem a little weaker than it should be(maybe.)

I will check it, thanks!

The spark should be a very bright Blue in color. Any other color indicates an issue. If not Blue, do an OHMS test of the coil.

Paw Paw

if it's a wasted spark system, you should get 3, 4, maybe 5 per kick.... 2 if you didn't remove the plug from the head.

Had an issue with getting my tc250 to start after having it apart before. Had to push start to get it to fire. Starts up fine with the kickstart now.

Just checked the compression, I only got a reading of 65 psi.

That was 65 without disabling the ADC.

Correction. The first readings I took were with the throttle closed. At WOT I got a much better 80 psi. That's with the ADC working.

I guess I don't know what it should be with the decompressor actuating. That would be very low for a four stroke without a decompressor. Hopefully someone here has the spec on what it should be with the decompressor working.

If you're getting spark I would think you'd at least get a pop or three using starting fluid at 80psi. Hell, the motor might spin a few revs or idle even.

I'm guessing you got a spark problem still- how many do you get with one kick? You've never come back and said (...and I would've done this easy test before the compression test).

I'm thinking weak spark.

i had a Yamaha with a dirty kill switch partially grounding once. I disconnected it and the spark fattened right up and started 1st kick.

i'd check and clean and grease all connections and maybe swap in a new coil and plug boot. They are cheap.

Has the bike seen much use?

Push start it