Yamaha Moto 4 250 oil consumption

[Diesel Dave]

Hi there, I am a new member and have never used a forum before. I own a 250 moto 4, has smoked since I got it.

Oil consumption has increased, I removed the crank case breather pipe and have a catch can under frame at front. Smoke has not changed. also after more than 20 hrs use during lock down there is a very small amount of oil come out the breather.

Compression seems very high, engine turns not too bad if stopped for up to 20 mins but much more than that it is difficult to turn engine past tdc. (poss almost hydrolocked?) if left for a couple of hours or more it then turns over easier. Also if spark plug is removed. I would have expected oil to come out when turning engine with spark plug out. 

I suspect oil is getting down valve guides? smoke is worst during warm up. The starter motor has not worked since before I owned it and I have modified pull start as the pressure on it was causing problems.  I am about to check valve clearances this morning before I get going.  I do not want to dismantle while lock down is on as I am using it daily.

Any help would be greatly appreciated, Dave

[Lance Workman]

What are your compression numbers? Whats the spark plug look like?

[Frank Angerano]

Probably going to be valve stem seals or a piston and rings.  (Maybe both) bit definitely going to need a compression test to see what's happening.  
Are you adding oil to keep up with the level ? Also what's the oil level? (Not over filled) is what I'm getting after. 
Lastly does the oil smell like gas? 

[Diesel Dave]

Hi there,  thanks for the reply. Spark plug looks good, I have checked the compression but only have the pull start.  I could only get a reading of 40 psi. I compared that to a Honda TRX 250 using kick start and found it was 50 psi, this one doesn't smoke.  I can't say how accurate my tester is as its an old one in my garage. I started the engine this morning, after 5-10 secs it was smoking pretty bad. I drove it for 2 mins and smoke had all but gone. I regularly keep an eye on the oil level, it requires a top up more than once a week if used daily. I have not changed the oil since owning it so will do that.  If no improvement I will have a look inside once the lock down is over. Do you have to go genuine for engine parts or can I get good after market ones online?

Cheers

Edited April 17, 2020 by Diesel Dave

[Frank Angerano]

Partzilla.com is great for atv parts and all schematics are on the site with manufacturers part numbers.   
Compression should be a lot higher then what your getting.  I would say minimum reading should be 90 pounds.   
Its going to be valve stem seals or piston/rings.