2 Stroke 1988 CR250R Wont start / Wet Plug

Ok so I just got this 1988 CR250R. I ran a half tank through it before it was obvious it needed work. It has been running really rich. Right now I can't get it to start, I pulled the plug and it's wet with fuel. I replace it with another new plug and it still wont start, wet with fuel again.

When I got the bike, I noticed it had a small fuel tank leak so I replaced the stock tank with a used Clarke. I cleaned it out really good, as well as the petcock and screen. I also drained and filled radiator with engine ice, changed engine oil (which looked like it had some gas in it), and put in new air filter (uni). I also rebuilt the carb with all new gaskets, vent and gas lines, new stock 185 main, and new stock slow jet. Needle is stock 1367 with clip in fourth position per manual. I set float to 16mm, air screw two turns out per manual. Carb is ultra clean. I have been running Sunoco 90 octane non-ethanol in a 32:1 mixture. I also repacked the muffler.
Bike just will not start. I put in a brand new denso (correct per manual), and it is just soaked with fuel after many kicks and not starting. I remove denso and replace with brand new ngk .... same thing. Will not start and covered in fuel.

I strongly believe whoever had this bike before me tried real hard to cure the rich running issue but ultimately could not. I found the carb to have a leaner main 175, and clip raised two positions over manual recommendation. When bike did run it spit black oil out of the pipe, hard to start, and only really ran ok wide open. The engine has all new gaskets and seems to have good compression.
Anyone know what I should do here?
Thanks!
I also need to rebuild the calipers, install new bearings, seals, etc (it doesn't end!)
 
Do leak test and a compression test to start. Low compression will show up first as a rich condition.
The leak test will help make sure your crank seals are good.
Then check the float height.
Make sure your coil is clean at all mounting points and the ohms readings are correct.

Paw Paw
 
Well I didn't see where the float height was checked, this could cause rich running and fouled or wet plug if not set correctly. But what concerns me is if there was gas in your transmission oil, I'm thinking either right side crank seal bad, or the case gasket had failed where the crankcase and transmission are separated,usually when crank seal fails the bike will still run, but blow LOTS of smoke and oil foul plugs, the failed gasket would allow fuel out of crankcase and into transmission, but if you got it running it would also blow a hell of a lot of smoke once either the seal or gasket failed, it would not only let gas out but suck oil into crankcase. Since you never saw the smoke when it was running previously, I would check your float level first, and set it correctly if needed. If this doesn't get ya going and you still believe there is fuel in oil, then you may have internal engine problems.
 
ok thanks a lot for the replies. I just took out the reed valve assembly and saw no damage. I guess I need to do a leakdown test? how is this done? not too difficult I hope.

I have about 900 in this bike at the moment. If the crank seals are bad (sounds pretty bad) is this thing even worth fixing? Also if crank seals are bad doesn't that mean the crank bearing are probably bad too? Man this is not looking good .....

It was running before I dropped the needle to fourth position per manual. There is just a shitload of fuel entering cylinder and fouling everything.
 
I just put a plug in the cylinder head, and one in the plug boot. I am not getting spark this time. This bike is so hard to kick over, there must be a ton of compression. Im 6'1 175lbs and I cant get a good kick on this thing at all. I can almost stand on the kickstarter and it would gently let me down. Its like I have 1000lbs of compression. I cannot generate a sufficient kick to create spark. Now if I remove the plug on the cylinder head and keep the plug on the boot and kick it, its easy, smooth, and I get lots of spark. Is it possible to have too much compression?? Any way to get a better spark out of a shittier kick?
 
The seals are not that hard to replace, but you do have to remove the clutch side cover, drain the oil and water, remove the flywheel and the drive gear from the clutch side. You can get the seals out with out too much effort and install new ones. The crank bearings are not always bad when the seals go bad. They are rubber and wear out.
The compression feels so high due to the excess fluids in the crank cavity from the carb flooding.

Paw Paw
 
ok thanks you made it sound like the seals shouldn't be too bad...

Though the compression has been this high since I bought it. I just changed the oil so I don't think theres a lot of extra fluids in there. No gas or carb in there either at the moment. A bad seal would make the cylinder flood with gas?

my foot is killing me. this thing has a shit ton of compression. im not kidding. I guess I need to buy motorcross boots? remonds me of being 10 and riding my friends YZ 490. I couldn't start it if my life depended on it, but I could ride it way better than him.
 

SRAD97750

Moderator
Staff member
I am actually starting to injure my foot trying to start this thing. way too much compression over here
Though the compression has been this high since I bought it.
my foot is killing me. this thing has a shit ton of compression. im not kidding

I know what you mean by the bruised and battered foot. Even with MX boots, I have had huge purple bruises trying to start my 89 YZ250. It has relatively low compression ~160psi.
But, You can't gauge compression with the kickstart. Never trust what you feel at your foot, it is very misleading.
Example, I can start my KX85 with my hand, it has 190psi compression.
The 'feel' is based on the mechanical efficiency of the kickstart mechanism.

Only a gauge can tell you, accurately, your compression reading.

I just changed the oil so I don't think theres a lot of extra fluids in there
In a 2T the transmission oil and crank oil are separate.
What you drained and refilled was transmission fluid.
The crank is lubricated with the pre-mixed oil in the fuel.-BIG DAN:thumb:[/QUOTE]
 
No, the excess fluid in the crank case is from the carb flooding some time back when you first having the running and starting issues. The bad crank seal will allow trans oil in the crank cavity too.

Paw Paw
 
?ok thanks a lot guys for the replies! I will order some boots today for sure. I remember seeing new fly maverik's for under 100 shipped. I will probably go that route.

at this point im left wondering if I should continue to find out why im pouring all this gas into the cylinder, or start tearing open the engine (which does sound a bit extreme at this point but I don't know). Again, the engine does have new gaskets all over, even oil filler plug is new. Waterpump cover and gaskets also new. Looks like a lot of work was recently done in there.

If I may revisit the carb again briefly. I set float height exactly per manual instructions using digital calipers to 16mm. The float valve set looked to be in perfect condition. Is the float valve supposed to fully close under it's own weight? Seems kind of weak. Any way to test the integrity of the float valve system? Again, parts look new, but I was concerned float valve needle possibly excessively weak as it fully compresses easily under the weight of the float alone. Is this normal?? :cripple:
 
When i have the float bowl off.....I attach the fuel hose to the fuel inlet of the carburater, then as I let the float drop I should be able to blow thru the hose, when I push the float upward towards the carb, the needle will stop against the seat and you will not be able to blow air thru, I repeat this a few times to make sure the needle is not hanging up or sticking. But this will let you know if the float operates freely and if the needle and seat works properly. One thing you might also want to check is, has the float sunk, in other words will it fill up with fuel when immersed?this would make the engine flood also.
 
In correct float bowel level is more of a running issue, or gas will flow out of the overflow hose. I believe he has plug/spark issues. Plug cap wire could be loose or not even connected in the boot. To keep your foot from all the kicking, keep the plug out of the head and push the kick start down with the plug next/on the head and se if you get a spark. Coil could be bad or plug could be dead. I wouldn't tear into the motor until you eliminate electrical issues.
 
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