I posted this question over at 2-Stroke World a few days ago, but so far...crickets...no replies. So I thought I'd post it here and see if someone here might be able to offer some ideas. Myself and a friend are restoring an RD400, and he recently rebuilt the oil pump using an HVC kit, as shown in the picture. After we discovered it was still leaking after the rebuild, he dried all the oil off and was able to pinpoint the leak at the gasket shown with the red arrow in the photos, the one with four screw holes. Here is what he emailed me today: "It is the gasket I showed you. Better description is that it weeps, not really a leak. Possibly a bad gasket that is porous? Nothing that I can tell is preventing the mating surfaces from full contact with the mating gasket sandwiched in between. The powder application was conclusive. She's a weeper. I don't see where gasket cement should be necessary." I did a thorough search on this, but all I saw were people who had a leaky oil pump that hadn't yet been rebuilt. Anyone else experienced this after a pump rebuild? Any ideas? Thanks in advance for any info. anyone can offer.
Silicone is NOT for use on gaskets , it's for in place of gaskets. Silicone is slippery and often allows the gasket to squeeze out. Gasket SEALER is for gaskets . You need an oil free gasket to start with again also.
joexr, thanks for chiming in and setting me straight, sounds like you know what you're talking about. I was going to order a new gasket tomorrow in any case. So is it ok to use gasket sealer on this gasket when it appears it's not required, and do you think it will improve the seal of the mating surfaces? I spoke to the guy who is working on the oil pump and he said that he didn't see any nicks, and also removed all gasket material prior to replacing with new. If the surfaces are a little uneven or not completely level, can the gasket sealer compensate for that? Thanks in advance for any further advice you can offer.
Yes , a little. Either brush it or smear it on thinly with your finger. Looking at the gaskey compared to the other one in the pic , it may be a porous gasket. Coat the edges of the gasket inside and out too. It may just be oozing thru the gasket. See what the two pieces look like together without the gasket.
Great advice, joexr, thank you. Guy working on pump already said it might be a porous gasket (not sure why they'd do that there), but we'll try the gasket sealer and compare the two parts beforehand. Thanks again!
Seems like Joe has got you on the right track. I am not a pro wrench but work on lots of 70's bikes and have found that you often have to go beyond what you think may be needed even with new parts. The proper gasket sealer should get you all set.
Thanks also for chiming in, klp. What you say about going beyond what seems needed certainly seems to be true in this case.
I'd be careful about getting gasket sealer in side the pump lest it plug a passage. I often use gasket sealer (Yamabond #4) on one side the gasket, the side that is removeable. For example on base gaskets I put the seal on the cylinder side. That way when it comes time to remove the sealer I can do it on the easily cleaned cylinders rather than on the cases where I have to worry about dropping pieces of sealer into the engine. Of course if you need to seal both sides to get the gasket to stay in place or to seal, you do that.
