250 XC 1985

[dr.fabi]

Hey everybody!
I just finished my engine rebuild end everything runs and works as hoped.
I got the cycle from a friend who took it apart 10 years ago. Now since it runs and all bearings as well as seals/gaskets are redone I observe the characteristics of the engine.
I have maybe 30 min running time on it and found oil spilling through the exhaust pipe.
It is just enough to produce a black film over the pipe and frame. I have to say that I tanked the engine with far more 2 cycle oil in the fuel (probably 3-4 times as much as required) to produce a good initial greasing. I have probably to much oil in the engine too. But there shouldn't be an internal leak since I rebuild the engine very careful. I did cut my gaskets from a sheet with a razor blade.
Does anybody know if this is a problem or a concern and has similar experience?
Thanks
Fabi

 

[Ron]

You can try sealing the pipe to the head with a high temp silicon sealer (Permatex works).
Use a quality 2 stroke oil at 32:1 will be plenty of oil for average play riding. But that's not a fix.

If your still getting a lot of oil coming out at the silencer (end is drooling), your jetting is to rich.
Most common cause of black spooge is the pilot jet is to big (very general statement, but true).

I'm sticking my chin out here, but while play riding we spend a lot more time in the closed to quarter throttle position than we like to think and that's where the pilot jet controls the fuel quantity.

Rich jetting cools the combustion chamber and prevents it from reaching a temperature high enough to burn the oil.

Always best to start with rich jetting and work toward best performance and light brown plug color.

 

[dr.fabi]

Thanks, I will do this!
Thanks for the advice.
Fabi

 

[fran...k.]

Ron gave you a pretty good write up. I filled up with some gas mixed with honda synthetic oil mixed at 32:1 or 16 oz per four gallon which I think is really the recommended ratio for a racing 80cc some think 250 or so would/should use less and it made goo out the pipe. I am not sure exactly what I will use this year but these don't have power valves which I was using the honda oil for.

If you have a problem with the gasket or the crank seal on the drive side most likely something suspicious will be observable at the transmission breather.

 

[dr.fabi]

Just a naive question (I'm embarrassed). How do I change the jet volume?
I did a very precise job with the gaskets. That shouldn't be it!
I believe now its the mix and ratio.
Thanks again

 

[Ron]

Pilot jets are specified by numbers ie: 30,35,40,45,50 etc. Larger numbers flow more fuel.

 

[fran...k.]

I do not know how to change a jet volume. To change the cross sectional area of the orifice you unscrew one and screw another in. Some insanely fussy or extremely cheap folks have been known to source out tapered reamers or fill them with solder and re drill but you then loose the numbering value. The bottom of the carb needs removed and there is an air jet and a pilot jet screwed in deep inside kind of holes. The main is the one that is a hex in the middle. I would imagine you either remove or rotate the carb. Pulling the slide out before rotating generally isn't as brutal to the cable.

Why not just mix up proper fuel and go riding? Oils do have different burn off temperatures, I suspect the honda synthetic is rather high.

Fran

 

[Old Geezer]

Why not just mix up proper fuel and go riding? Oils do have different burn off temperatures, I suspect the honda synthetic is rather high.

+1 on that. The tendency is always to go on a witch hunt for all the many dire possibilities. You mentioned 3 to 4 times the normal amount of premix oil was used, so what...you're running at a 10:1 oil mix or something like that? Way way way too much oil and by the way, that will also affect air-to-fuel ratio to the lean side as well which is not good either unless you adjust the carb to compensate for it. Surprised your plug hasn't oil fouled yet.

Fresh gas, 28 or 32:1, go for a ride.

 

[suprize]

If your using a fully synthetic oil, you can go as high as 60:1 safely. Im using 80:1 with Motorex oil and have 3 years on my 010 ktm 300 thats just had its first top end rebuild! this runs more fuel per charge and the engine runs cooler.
I have run it as high as 100 :1 and i have it leaned out nicely so it just has a slight 4stroke at even throttle.
The motor is like an electric one at very low revs and never coughs out or snap stalls in those tricky rock / log crossings situations were you are perched precariously for a moment and thats when the stall seems to always occur.
Oh yeah, i run the WR400 on that same mix. i recently rode a 20 min loop with no water in the rad when water pump seal repair failed and didn't realize this until it was pointed out that the water was pushing the gbox oil out the breather The motor didn't seem all that hot which was interesting and possibly due to the cool fuel mix which helped it survive. I havent started it since so there may be a few issues im unaware of as yet

So the sum is i have no sploooge issues unless i ride in very tight stop start conditions for 30 mins or more (goat track on the side of a hill type stuff) then a dribble may appear or its smokes like a chimney on its next hard run.

30 or 40 :1 is the right ratio for standard or semi synthetics and splooge is usually minimal with these ratios but generally will run out if pipe fittings are not well sealed.