Mini TRX Engine "catches" When Rolling

[goodwick]

My daughter flipped the go kart and caused the pull start to get jammed. I pulled the casing off and was able to manually turn the engine with a socket, put the cover back on, and after letting the engine settle, it was working. After that I changed the oil, added fresh gas, test rode and it was fine.

Fast forward to a week later, we went to go start the go kart, started up, she drove about 10 ft and it shut off and I couldn't get it started again (pull still works with no resistance). Now when I roll the go cart (manually) it gets "caught" and there is resistance after 1 full turn of the fly wheel. You can visibly see the clutch get temporarily jammed then keeps rolling.

I took off the clutch today, cleaned the parts, degreased, added white grease thinking that it was just getting jammed, but I am still getting the same result. The clutch rolls freely until I attached the chain, then you can start feeling the resistance (and it still doesnt start). I think something might have happened internally in the engine? Any thoughts or hacks here before I go down the rabbit hole even more?

I am pretty good at working on these things, but I don't want to have to rebuild this thing unless we absolutely have to. Any insights would be appreciated!!

 

[Whitetrashrocker]

Send pics of the general kart and maybe some close ups of the troubled areas. We have x ray vision and can for see the past.

Possibly bent axle and the chain is binding?

 

[Master Hack]

Sounds like something got bent. WTR and x-ray vision have a 93.6% success rate!

 

[JimD]

Does the engine run without the clutch on it? You indicated it ran after you changed the oil, and ran good for a week and then you had problems. That does make for a challenge with the experts on the site but they do love a challenge. Let us know if the engine run with nothing on the crankshaft. If the answer is yes it run fine then we know better where to go but I am guessing something came lose inside the engine and is jammed under the crank possibly a disconnected piece of plastic from the governor but still to early for guesses until you tell us if the engine is still running.

 

[goodwick]

cant get it started now, but the pull start works without any resistance. check out this video and you can see the clutch "catching" every so often. I agree with a lot of you and something got messed up internally. let me know what you all think, Im ready to start pulling it apart

mini xrx vid

goodwick.my.canva.site

 

[Master Hack]

The first few seconds it looks like that clutch bell is bent. I cant tell for sure. You might look closer at that. Do as Jim suggested.
Pull the clutch and see if the chassis rolls better. Try and start it without the clutch/chain.
pull the spark plug. Put yer finger over the hole, pull the rope. Do you feel any pressure?

 

[JimD]

Buy some typewriter white out - someone has to use up that stuff besides me. Two things I want you to mark -the brake disc and the chain. You are doing this to see where you are getting the bind at. Lets say your ration right now is 6:1 (10 tooth clutch and a 60 tooth axle sprocket). The clutch will make 6 revolutions before the axle sprocket makes it first complete revolution. You will be painting the chain and the sprocket where you get the bind to see if it hits at the same spot every time. I like to paint a 360 circle on the brake disc on both sides to see if it is rubbing one side or the other which will tell you it is bent which you should be able to see but the paint will tell you for sure were it is rubbing. You have put the rear bumper up on box so you can sit and rotate everything in place very easy and do your marking. This will also tell you if you stretched the chain because that will always hit in the same place telling you that link is bad.

Will not start is a good indication that the flywheel may have sheared the woodruff key (half moon key) and has advanced the timing which will account for it not wanting to start at all.

Take the spark plug out, just makes it easier turning over the engine. Was the governor disconnected on the engine? And were the inside guts of the governor removed which I know will fly apart over time and get jammed in the worst spots and blow the bottom out of an engine but that is what JB weld is for and best of all, we learn by our mistakes.

I guess the other pictures these experts will want to see is more of the jackshaft that the chain is going to which has nothing to do with the starting problem put could has some answers to why you are getting the bind. That would make the ratio I gave you up above not accurate at all since there is a jackshaft involved which I didn't catch until looking at the video a second time. Oh well, shows my age.

 

[goodwick]

Took spark plug out, and I can feel pressure when pulling the rope. I took off the main chain (to drive wheel) and when I push the cart, there is no more resistance, which leads me to assume its in the clutch or flywheel. Still can't start it without the main chain on, I can hear it trying to turn over but nothing. Replace or rebuild?

 

[goodwick]

here's a video (link) of what I was seeing today. Trying to hand turn the clutch and there is a spot where it "sticks", then turning it over with electric start. let me know what you think. Pic of fly wheel attached too, looks good and when I manually move it, I get the same sticking. I also took a magnet into the crank shaft (pulling spark plug out) to see if there was anything on top of the piston, but just pulled some carbon build up.

go cart vid round 2

goodwick.my.canva.site

 

[Whitetrashrocker]

Pull the flywheel. It might have sheared the key way.
This would cause the spark to not be at the right time.
That tough spot you feel when pulling over might be just the normal compression.

 

[goodwick]

Pull the flywheel. It might have sheared the key way.
This would cause the spark to not be at the right time.
That tough spot you feel when pulling over might be just the normal compression.

I'll do that this week and send pics and let you know what I find, thanks