I opened up the top in on the DS 80 I’m working on and discovered that it needs attention.
Looks like it will need a bore and piston.
Using a caliper I measured the bore at the top to be 45mm which according to the owners manual is the standard bore. There are no markings on the existing piston other than the arrow. There is a +3 marking on the top of the cylinder.
Hodaka Parts, Inc. has pistons in stock but the photos show pistons with the holes in them that I thought were for a reed valve setup.
I’m wondering what size piston I should buy??
If the scratches aren't too deep you should be able to salvage it at 1st over. Might be better to ship the cylinder to HP and let them bore it, that way if it does need to go to 2nd over it'll be easier for them to grab the piston and do the work.
Thanks, I’ll probably do that.
Any idea what would cause wear like this? The top of the piston and head had a fair amount black carbon.
I know little about the bike’s previous life. The oil injection had been removed. It looked like it was done correct with a plate over where the pump was and a plug at the intake. The first thing I did was drain the gas (that appeared to have oil) I put in fresh non ethanol at 32:1 Yamalube 2R. The main jet is a 65 which according to the manual is the “standard”. Clean and oiled air filter when I got it. Intake system seems to be tight. The bike started easily and seemed to run fairly well, although all I did was run it up and down my driveway a few times.
I don’t want to put a new piston in and have it go bad.
Victor,
I think that is a reasonable SWAG. When I got the bike last month it had a new looking air box, boot and filter. That makes me wonder why it was replaced and how bad was it and for how long.
If that’s the case is there likely to be damage to the crank? Am I looking at possibly a full rebuild?
Bob
If there is no play in the crank bearings and the bearings roll smoothly with no rumble, it should be good to go. On the flip side the only way to truly know it's good is to rebuild the crank and run it in new bearings. Of course renewing the seals is a given.
What Thrownchain said! If you have the cases apart, & the crank out, give it a good inspection. Does the rod “wiggle” in directions it shouldn’t? Is there visible signs like on the cylinder wall of scratching? If you decide yes, there are several folks who can do the crank rebuild for you. Hodaka Dave, California Hodaka, Danny Cooke, all good resources, and depending on where you live, pick one! Victor
Victor