Clutch side crankcase seal?

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

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

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

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

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.

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

Thanks.

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.