Newbies Forum

I had someone give me a yamaha mx175, trail bike. It has been setting for quite sometime, and I'm trying to get it running for my cousin who is 12 and have put new needle valve assembly in it and, put rings in it, cleaned the tank fresh fuel, and gasket kit. It will start, but seems real boggy, and can get it to go but then it dies. its oil injected, and when you stand with it started you have to the throttle it, and its throwing black soot out the exhaust when its revved and eventually shuts off. My cousin is really anxious to get it going but I cant figure out whats wrong. The damn kickstarter just cracked and need to get 1 of those, but yeah I need help. If anyone can help I would appreciate it. Thanks !!  

How does the plug look?  Also, have you cleaned out the pipe and silencer?

Be careful with those oil-injection jobs.  The injector hose tends to get clogged up very easily - personally, I'd bypass the injector and just put 32:1 premix in the tank.  
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Here we go again!

Thanks for the reply, yes I checked the plug it is wet and brownish black color which I think its running rich, How do you by pass the oil injection ?? I cleaned the front pipe, but not the silencer. Its a 79-81 year model and found the oil injection pump, and it seems to run alot better with the air filter box cover and filter off ?? but still cant get it to take off, also can the kickstarter be welded or do I have to get another one.  Thanks, Josh  

Shouldn't weld a kickstarter.

It's DEFINITELY rich!  I'd start by dropping 2 sizes on the main and see how she does.

The best way to bypass oil injection is to disconnect the injection pimp (linkage if it's mechanical, wire if it's electrical), and then plug the hose where it goes into the motor.  From there, just remember to fill the tank with premix.  
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Here we go again!

The injection pimp. 92?  

Ok its got a wire, at the pump, I thought maybe the oil injection lubricated a certain bearing or something in the bottom end. I will disconnect it in the morning and then premix her. Ok my neighbor is a welder for the railroad and he said oh yeah we can fix that, but that was with a couple of coors light in him, lol. and also its leaking oil out of where the oil injection pump is, out of the cover and was wondering is that escaping to the engine making it run richer, also maybe a cracked line from pump to crankcase filling up the cover and forces it out ?? hopefully I'm not being too much of a pain with this lol, my little cousin is very, very, anxious 2 get it going. Thanks again  

The carburetor may be adjusted way out from where it should be.  The flat head screw on the carburetor is the pilot air screw, try turning it in until it lightly bottoms out then back it out 1-1/4 turns.  This is the factory setting for that bike and assuming it hasn't been re-jetted should get you close.  The idle screw is bigger and can be adjusted with just your fingers.  I hope this helps.

I agree with skipkh regarding bypassing the oil injection, it's a good idea on an older bike, my mx175 has the system removed.  

sledrider84:
I had someone give me a yamaha mx175, trail bike. It has been setting for quite sometime, and I'm trying to get it running for my cousin who is 12 and have put new needle valve assembly in it and, put rings in it, cleaned the tank fresh fuel, and gasket kit. It will start, but seems real boggy, and can get it to go but then it dies. its oil injected, and when you stand with it started you have to the throttle it, and its throwing black soot out the exhaust when its revved and eventually shuts off. My cousin is really anxious to get it going but I cant figure out whats wrong. The damn kickstarter just cracked and need to get 1 of those, but yeah I need help. If anyone can help I would appreciate it. Thanks !!

I had a MX175 back in 1979.  I know you put rings in it, but did you have the cylinder checked for wear?  Also what shape was the piston in?  When you kick it; does it have decent resistance or is it easy to kick (indicating poor compression)?  
Dave H 2006 YZ250
(2008 YZ 125 son)