SlammedRanger

I would start with the easy fix. Unscrew the yellow cap the plug boot comes off lefty loosey righty tighty. Cut about 1/2 inch off and screw it back on and test again. That is the easy and most common fix. If it doesnt you got just a few options. You can test coils. It is all about resistance. You gotta have a tester that can test for resistance. But my experiance is testing them doesnt really tell you much. I have had them test bad and be good. And test good and be bad.

Well the general rule of thumb is anything 100 or over will run. Maybe not perfect. But it should pop off. If starting fluid didnt get it to fire you most likely have a spark issue. Pull the plug and put it back in the boot and hold it against the side of the engine and look for a fat blue nice spark. If its orange or tiny there is your problem right there. I do suggest having a fire extinguisher on hand and ready. Just incase the engine has gas on the top of the piston and comes pushing out the top and it could ignite. At that point we can look into spark components.

If the jets had the K on them its a very good chance that is the oem carb. China carbs dont come with jets with the K on them or atleast not that i have seen. Niche is cheap. But i had a buddy that we put the piston and jug from a niche kit on his quad and it ran no problem at all for about 3 years. Now the concern would be if they sent you the wrong size piston or something. Not matched for the bore size maybe? We mic'd everything and ours was close. We did end up running a hone through the jug a few times as it was a tiny bit too tight for our liking. But would have ran im sure no problem.

Yep keihin would have been the oem carb more than likely. But even that isnt a guarantee anymore. China carbs have been selling with keihin and mikuni castings on them now. The only way to know for sure now is to go off the part numbers on the side if the carb body.

@DeadBattery i us jetsRus. They will have everything you need. If you had the oem carb i could tell you exactly what jets it has. But china carbs can be all over the place. You will have to remove the jets and take pictures.

Ok lobes facing down was right. Did you confirm the piston was all the way up? 4 stroke engine so you will see the |T at bottom dead and top dead center. If piston wasnt up at top you would have it timed 180 out. But it would have never ran at all that way. When its timed 180 out it will pop every single revolution and not start period. Not a bad idea to confirm 100% but if it ran i would bet its not that. My bet is the jetting is whats causing you trouble. I was running a 45 pilot when my quad was only a 416 with a cam. It wouldnt even run on a 42 no matter how hard i tried. Just like your having happen.

SlammedRanger checking in lol. Ok so since rebuild it started with a valve tick. Then stopped. You said it was timed a few teeth off. Thats very scary. These are interference engines. Meaning valves will hit piston very very easily. (Few teeth off). You may have gotten lucky with that. 110 psi compression is also scary low. But valves being adjusted too tight could cause that. Also could be a bent valve. Were gunna hope for the best on that aswell. When you timed it did you have the cam lobes facing up or down with piston at top dead center? (On the |T mark on the flywheel.) The carb is also jetted not even close. Your gunna be a 45 pilot jet minimum. Possibly a 48. And somewhere in the 180-190 range on main jets. With the 440 kit. Did you ever confirm where the metal inside the engine came from? Thats scary aswell. Usually metal shavings on these engines are crank failure.

Is the new starter doing the same identical thing? You can try taking the battery and putting jumper cables on it and touch a ground and a positive to the side post on the starter. If it turns over smooth then you only have wiring, the solenoid, and the start switch in between the two. I would personally never run 87 in any atv or dirtbike. 93 is minimum. Probably even says that in the factory service manual. How high of compression you plan to go will decide what fuel you use. (10:1-11:1) 93. (12:1-13:1) 100 or 110

After alot of research and saving my side cash i picked up a little pitbike to rip around the yard on and race the daughter on her trx90. Even tho it looks like a honda crf110 now. It is actually a 2022 thumpstar tsx125. Not a dirtbike guy and it shows. Daughter on her 90 can almost beat me around the yard haha.

Thats awesome THH! We all really appreciate that for sure! 1 more of many reasons this place is so great!

Sounds good! Keep us posted! We are always happy to help!

In my experiance the db electrical one is maybe 20 dollars more than a china cheap-o. But they are the ones everyone swears by. And i have one on my quad and its been on it for about 4 years. Zero issues.

Ok good. Thats good news. The starter is gunna just be tired then. You can pull them apart and rebuild them. But honestly i would just get one off ebay from db electrical. Stay away from the super cheap china junk ones. They dont last.

Ok what i would do to start is take the plug out of the side cover and turn the engine over by hand with the 17mm bolt. Make sure you only turn it counter clockwise. Make sure it turns freely. You should have some compression to push through but it shouldnt be really hard to turn a full revolution. The starter can get hot for a few reasons. Engine not turning over smoothly or the electric motor is getting worn out. We want to be sure its not engine binding up.

Welcome to the forums. When you say its getting hot. What part is getting hot? It does sound to me like your starter is on its way out. Cranking slow can be an indicator of that. Saying the battery is fully charged.