Clutch side crankcase seal?

[wildkats]

Hi All,

I've got a some questions on a problem with my RM125 flooding, fouling, and not idling.

Here's the situation: My 94 RM125 (bored to 147) is constantly flooding the cylinder and fouling the plug. I brought it to a Suzuki service location and they 'tuned' the carb and changed the plug. I brought it home and it would start and idle but then after a few days of running it for a few minutes out on the street to check that it still worked it started to flood and foul the plug again.

Now the service dept tells me that the Crankcase seal (clutch side) needs to be replaced.

Here are my questions:

1) Are they full of S$#% about the crankcase seal? Can someone give me a simple explanation as to why that can cause the flooding and idling problems? As you can probably tell, I'm very new to 2-strokes.

2) Could it be that I'm not warming up the bike enough? When I'm at the track I always hear 2-strokers run their engines for about 5-10 minutes to warm them up. I just run it for maybe 1-2 minutes.

3) Which seal is the mechanic talking about? Is it the oil seal on the crank shaft on the clutch side or the crankcase gasket? Anyone know the part number?

4) Do I really need a crankcase separating tool to split the cases or is there some rig I can use with regular tools? Same goes for the crankshaft oil seal. The manual says to use a special tool. I'm thinking just a screwdriver to remove the bad seal and a socket to install the new seal.

5) Last but not least, does anyone have suggestions as to what jet sizes and air screw settings to use for my setup? I noticed that the main jets are already 3 sizes smaller (leaner) than stock.

Sorry for the long post but details make all the difference!

Thanks!!!!

Delius

 

[wildkats]

BTW, I already checked and cleaned the carb, replaced the air filter, checked cooling hoses/radiator for leaks, replaced the coolant and tranny oil with Honda 4-stroke 10-40 weight.

Thanks again.

Delius

 

[MadArrow]

What size pilot jet and what clip is the needle in? Those two usually have more to do with fouling then the main jet. Expecially if it is already 3 sizes smaller which sounds awfully small to me. It sounds like more of a jetting problem to me. I think a bad crank seal would make the bike run leaner. There are a couple of really good guides about jetting on this forum if you do a search.

 

[nickyd]

the seal that you are speaking of (on the clutch side) can go bad and cause a leak - in this case, the oil for your tranny/clutch can leak past the seal and into the combustion chamber - the extra oil can cause the plug to foul. what does the plug look like? lots of carbon?

you don't "NEED" the crankcase tool, nor do you "NEED" the seal driver - in fact, you don't need to split the cases to fix that seal. it can be pried out and replaced by just removing the clutch side components.

 

[wildkats]

Thanks guys.

The plug doesn't look like it's got carbon on it. It's just wet with gas/oil and after cleaning it, letting the fuel evap in the cylinder and putting the tip under some fire (as a friend suggested) it starts fine. I've also checked the spark and it's nice and bright. Also compression seems fine per the same friend and the mechanic at the dealer.

I still don't get how a seal that keeps dirt out of tranny at the crank can cause tranny oil to leak into the cylinder. But then again I'm not a mechanic and obiously don't know jack about engines in general.

Let me see if I understand it right, on the down stroke some tranny oil is leaking past the piston rings into the chamber thus fouing the plugs? And that's because the crank (the part that the front sprocket is connected to) seal is leaking air into the tranny?

One thing I did not check was the reeds. Can that cause a rich mixture also if they don't close correctly?

Delius

 

[nickyd]

Thanks guys.
Let me see if I understand it right, on the down stroke some tranny oil is leaking past the piston rings into the chamber thus fouing the plugs? And that's because the crank (the part that the front sprocket is connected to) seal is leaking air into the tranny?
Delius

Not quite - the way a two stroke works is by changes in pressure - when fuel enters your motor (through the reeds), the fuel/oil mixture needs to find its way to the LOWER end (where crank and crank bearings reside) - through pressure change (low to high, high to low - I can get technical but I won't), the gas/oil is "sucked" up through the transfer ports of your cylinder (the run along side the cylinder) and into the combustion chamber (above the piston)....NOW, if the SEAL that is on the clutch side of your bike fails, Tranny oil, will enter that same LOWER end and get "sucked" up the transfer ports and into the combustion chamber, hence a rich mixture, hence fouled plugs.

 

[nickyd]

I just re-read your post - the seal that we are talking about Seals the CRANK area from the rest of the bottom end (the tranny and clutch). You understand that the piston/crank are separated from the tranny/clutch, right? if not I can explain

 

[psalm3124]

Had a leaky oil seal problem on my 02 YZ250. Went through getting adjustments etc. Nearly went crazy til some on this board helped me out.

I don't know how similar it is to your RM. But if they are similar, when you remove the right side cover, wiggle the crank shaft. There should be absolutely no play. If there is, the bearings need to be replaced. If there is no wiggle, then you just replace the seal.

As said above, for seal replacement you do not split the cases. To seat the seal, find a socket that's the same diameter as the seal and drive it in evenly.

If it's the bearings, the cases need to be split.

Hope this helps.

 

[wildkats]

It's like a light just went on. I now remember from a while ago that 2 strokes does use the space below the piston to store the fuel/oil mix and on the down stroke it gets sucked up to the top via a transfer port.

So the oil seal in question is not the one for the shaft that one would connect the front sprocket to but rather it's the one for the crank that sits behind all the clutch plates?

Am I getting closer?

Thanks again.

Delius

 

[darringer]

Yes, you're getting closer. Actually, the seal is directly behind the primary gear. It bolts to the right side on the crank. It is very common for this seal to leak on the early RMs (late 80's, early 90's). The primary gear is the gear that drives the clutch/transmission.

 

[wildkats]

I will attempt the replacement of that seal as soon as the part comes in. I'll post the results when it's done.

Thanks everybody.

 

[wildkats]

Do I need to get a tool to hold the clutch basket or is an impact wrench good enough?

Thanks.

 

[nickyd]

a penny in the gear works well.

 

[wildkats]

OK now I'm stating to get pissed. I've changed the clutch side crank oil seal. Bought a Motion Pro clutch tool to hold the basket and incidentially it works well for the gear that holds the crank too. Couldn't find a oil seal removal tool so I used a flathead.

Anyhow, replaced the seal (punched it in with a 3/8 extension), put everything back together, refilled it with 10w-40 bike oil, and refilled the coolant. She started up right away (always did) with noticeably less smoke, idled for about 10 sec then died and fouled the plug again. :bang:

I've taken apart the carb and the pilot jet is already the leanest it can be for a stock motor. Keep in mind that the motor has been bored to 147cc so it may need to be leaner. I also noticed that the needle is bent and the part number on the needle doesn't match the part numbers listed in the service manual. I've also checked the reeds and they close properly.

So now I have three questions:

1) What's the torque value for the clutch spring bolts?
2) On the needle there's a rise near the top. Is the outside diameter of the needle measured above that rise or just below it?
3) Is it true that because the engine is bored out it needs to run that much leaner?

Thanks again. I hope this thread helps others.