250r good spark no start problems.

[gimmeamidget]

Picked up a rough 1st gen 250r and has good spark. Tank is clean and had been running within the last year. Guy said it was running strong and just stopped. He thinks it sucked a ring. Has good spark and seems to have good compression ( I have not messed a lot with 2 strokes and don't have a compression tester) but feels like more compression than my water cooled 250r that runs strong. I kicked it over many many times and every now and then it gives a little pop like a backfire out the pipe. Maybe every 10th kick. Before I tear into motor can anyone lead the blind with ideas? Seems like a timing issue to me like maybe the key that holds stator timed gave out? Any help is appreciated.234324234325

[yaegerb]

Need to perform some tests to see what you are dealing with or spend a long time with trial and error.

1. Buy a tester and perform a static compression test
2. Buy parts needed and Perform a crank case pressure test
3. Perform a squish test
4. Examine reeds for flatness and no cracks
5. Ensure gas is in the float bowl of carb (check by cracking the drain tube). Check that plug is wet when kicking it over
6. Ensure air filter is not clogged or dirty

That should get you started. Report back what you find on those tests.

[RubberSalt]

Get a new spark plug
Make sure the flywheel isn't spun(broken keyway).

As for Yaegerb's 2nd statement. This is referred to as a leak down test. Very very very important. 2 strokes will burn up if you have leaks! Test the machine and the tool! You can make them dirt cheap. I've made them for less than $4. I'd recommend building one with a low pressure gauge on it. This way you can meter the air pressure over time.

[gimmeamidget]

Guys I will follow up and report back as I have time to tear into it. Thanks for the info.

[gimmeamidget]

234333Pulled carb and reeds all look great. Pulled stator cover and key was good but seemed to easy to turn flywheel by hand so pulled top end and piston was melted and rings were seized. Question is I noticed guy had put bottom ring on with print mark facing down. I believe print mark on both rings face up. Could this have caused the meltdown? Guy said bike only had few hours on new top end.

[yaegerb]

Ring faceing depends. If the kit doesn't tell you which way they face then numbers always go up. More pics would be helpful in determining what happened. Take a pic of the top of the piston and underneath the piston and on the sides. Also take a pic of the head and inside the bore of the cylinder.

When you say you pulled carb. Did you pull it and it looked nice on the outside or did you actually take the carb apart and look at the needles, needle jet, etc for obstructions and cleanliness?

[gimmeamidget]

234335234336234337234338234339234340234341More pics of piston.

[gimmeamidget]

Bore don't look to bad, hard to get good pic but I think rehone and may be ok. Some aluminum transfer but I think hone would clean it up?

[yaegerb]

I think you got sold a bag of beans. That piston has a lot of hours on it. I can tell by the carbon build up on the under side. I am guessing you will need more than a hone. Call John tice.

[RIDE-RED 250r]

No piston wash whatsoever, she was lean for one reason or another... But strangely, no melting/erosion of piston crown on the exhaust side. Some degree of that usually occurs with a lean burn down...

[DohcBikes]

2 stroke or 4, what you are showing is a lack of lubrication.

Upside down rings are no good.


Your bore might be fine. Muriatic acid applied to the affected areas with a cotton swab, let it sit for a few minutes then clean it off, rinse with soapy water and dry.

Have your bore measured by a qualified cylinder machinist.

[RIDE-RED 250r]

Think it was straight-gassed??

[DohcBikes]

Think it was straight-gassed??Very possible.

[atc300r]

Crank seals should be replaced aswell as topend gaskets.Looks like a decent first gen.

[RIDE-RED 250r]

Very possible.

Or possibly was run with some miracle working, wizz-bang 100:1 premix?? I dont want to take this to the oil and premix ratio debate, just throwing ideas out there....

[gimmeamidget]

I personally always mixed rich even back in the 80's. I still run 32:1 even with today's better oil. I was surprised you guys mentioned straight gas because the very small amount in the tank when I got it looked clear...very possible no oil mix. I plan on new top end and go from there. I gave the guy $250 not running and guy thought it needed new top end. I actually hope it was just straight gas that caused this and not another problem so should be good after new top end. Thanks for all the help and opinions.

[yaegerb]

I use Honda 2 stroke oil and it mixes clear with the gas. I hope to god he didn't do that because you will have more problems than just a top end. Have you checked up and down play on the crank yet?

[gimmeamidget]

No up down play and just slight side to side. First thing I checked when top came off. Shifts smooth also. I really didn't want to tear into the bottom.

[gimmeamidget]

I thought the crank bearing was lubed from the bottom? Even the wrist pin and bearing seemed good.

[yaegerb]

That's good on up and down. Have you checked side to side with a feeler gauge and compared to tolerances in the manual?

Crank bearings are lubed from the oil mixed with the gas.

Get a new wrist pin and small end bearing with your piston. It's cheap insurance.

[RIDE-RED 250r]

And if you decide to just do the top end without replacing crank seals and bearings, (bearings do wear over time and sloppy bearings will lead to leaking seals) I would strongly urge a leak down test before running it. Even if you do end up deciding to replace crank bearings and seals, it's good practice to conduct a leak down test to make sure everything went together right and seals properly.

A leak down test will let you know if there is any air leak at the intake, cylinder base, and crank seals. If there is a leak it will suck air and you will be pulling the top end again

[gimmeamidget]

Ok will do. Thanks

[gimmeamidget]

Got it up and running and now it fires up first or second kick. Went easy the first 4 short rides following the recommended break in....first ride less than half throttle but varying for 10 minutes then cool for an hour. Another 10 minute no more of Han half throttle and cool for an hour. Actually sat overnight got too late to run it. Next ride was 10 minutes no more than 3/4 throttle and cool. Then up to full throttle but still going kinda easy for the first couple tanks. A few things I noticed are it seemed to run hot the first 2 rides and I was disappointed in the power even though I could only go half throttle it was really lacking compared to my 85. I was going to get on here and complain about the gutless power. I decided to wait till I could open it up and see. It really seemed like by ride 4 the power had increased, and I don't mean because I could give more throttle but even the half throttle felt stronger and idle picked up. I am still considering going down a few teeth on the rear sprocket since I find myself trying to up shift when it is already in 5th. That 6th gear they put in the gen 3's is really nice.