Vintage Dirt Bike Q & A

Hey guys I just read Loren's post about his air leak and it convinced me to make some plates and seal off the intake and exhaust ports to check for any leaks. Last season I had a proplem with the bike pinging and running consitently lean, or just run bad when jetted richer, but it would never rev up, or idle high, or show any signs of an air leak. However I plugged the cylinder and put about 10 psi in it and I do have a slow leak around my left crank seal. It was replaced a year ago with an OEM Honda seal, and my guess is that it leaked slightly from the beginning. Also, is there any trick to getting that seal seated square inside the crank housing. If you push it in until it stops it will be pressed against the left crank bearing and blocking the small hole in the transfer port to help oil the bearing. But if if it is pressed in only part way its hard to keep it perfectly straight. I need to get this seal replaced before this weekends race in Florida and I don't have time to order one from the dealre so I hope the local hydraulic seal warehouse will have one. Is there any problem with leaving the engine together and pulling the old seal out and puting the new one in with the crankshaft still in place.

Thanks for the help,
Matt

Hi Matt,

I used a 1.5" PVC coupling and a small rubber mallet to seat the left main seal. You should be able to get the old seal out without splitting the cases. I've never done it without splitting them but that's because I've always had to split the cases for other reasons and just replace seals while I'm at it.

Just thinking out loud here but you could probably run a couple of long sheet metal screws into the existing seal and then attach something to these to pull it out. If you can get long enough screws that reach above the end of the crank you could put the stator bolt in the crank, use a piece of flat steel over the bolt head and span across beyond the sheet metal screws. Drill a couple holes in this plate, run the screws through this and then into the seal. Now if you wrench the bolt out it will push against the plate and *hopefully* pull the seal out.


BTW, my engine has been holding 10PSI for over 10 minutes now. Think it be good to go.

HTH,

Loren

_________________
Those who can make you believe absurdities can make you commit atrocities.

Loren Davis
51y

Hey Matt,

I went to your web page... Like that Rickman Zundapp. Especially that rear suspension unit. Design that yourself did ya???? Senior project in engineering school??? I don't think you'll have any problem conforming to the 4" rear travel rule.

Cheers

_________________
Those who can make you believe absurdities can make you commit atrocities.

Loren Davis
51y

I liked that mod too, I found the Rickman in the back of a barn, must have been farmer engineering. The rear brake pedal has a washer welded to it and some weld spatter on top for grip. I had everything planned to have it done for the Spring, but I haven't heard back from Lynn Wineland in CA who I sent parts order to. Does anyone know how he's doing, last email he told me was on going into the hospital for a transfusion and would get my parts together when he was out. I hope he's ok, I havn't been able to reach him. I ordered a left crank seal, next day air, so hopefully I can get that new seal in and have a good weekend of racing. Hey Loren, how far in does your seal sit from the surface of the casing.

Matt

Matt,

My seal actually sits inside the housing a bit. I drive it in until both lips of the seal have contact with the surface of the crank. If it sits flush with the top of that rise in the case I only have full contact with one lip of the seal. Shouldn't be that way but that's what I have to do.

Let me know if you ever get out to a west coast race. I'll let you take this thing for a ride.

_________________
Those who can make you believe absurdities can make you commit atrocities.

Loren Davis
51y

I tapped my seal in flush with case.....then added a thin washer over crank against the seal .
I then tapped the washer and seal in flush again, using a sturdy straight edge.
This had both lips sealing on crank.

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'84 Honda CR500
'84 CR125
'85 KX125
'83 IT490
'82 Maico 490
'80 YZ465
'75 Husky CR360 GP Mikkola
'75 CR250
'72 DT2MX
'91 XR200