Venus 50 (Now 96cc!)

[90GTVert]

I pulled it back apart to check some stuff out tonight. I didn't see any signs of contact like the piston was hitting anything in the crankcase or something like that, but it is lightly scuffed, as is the cylinder.





This cylinder was honed just before I tore T2 down, and a new piston kit was installed. All in all, it might have 45 minutes of run time on T2 and this. Never been driven on the street, just idling and testing in the yard. The ring end gap on the top ring was .025" and the second ring was .012". Both are too wide, the top by a long shot. I'm thinking maybe I was hearing piston slap? Thats what it sounded like and those gaps are pretty far out. I woulda thought I'd see more evidence of contact, not just scuffing though? Bore diameter looks good top and bottom.

Conrod small end, wrist pin, and bearing are all tight and within specs.



I can fit a .020" feeler gauge in here. The side to side play at the small end is about 1.5mm. I don't really think I need a crank replacement.



I'm thinking a set of rings might be all I need. Not really sure why it would be wearing them so fast. Maybe I was off on my mix ratio or something?

[190mech]

Can you feel any up and down play in the lower rod bearing?Whats the cylinder to piston clearence?(check with feeler gauges,stack thin ones,dont go over .003" as they are too stiff to bend to fit the bore contour)I'd say .006" is 'slap wore out'!
The bore and skirt are badly scratched like some hard stuff got in there,sand or steel filings,bet its the latter as the lower rod bearing gave up on T2 didnt it?The steel particles imbed into the soft piston skirt and act as sand paper on the bore,cant get the stuff out of the skirt without removing too much metal,likely best to replace the piston too..Also how is the skirt to case mouth fit?Had issues with bigger pistons touching the case step causing noise before...

[90GTVert]

There is no up and down play in the rod bearing, forgot to mention that. Haven't checked the piston to cylinder clearance. Yes, the scratches are from T2. The oil coating the walls looked like glitter wehn I tore it down the last time. It didn't look like the piston was hitting th case. That's what I was kinda thinking at first was that it went down too far or something. I moved the crank back and forth as fast as I could and couldn't hear any nose with the piston installed... of course I can't put the force and speed to it like it would have running. I would still think there'd be at least some light marking if anything were hitting.

EDIT : Piston to wall clearance is about 0.0045". I can't really find just rings, so the piston will be replaced anyway.

[190mech]

I'd replace the piston too,and get a good cross hatch on the bore.Here is just a ring set if you want to try that first;
cgi.ebay.com/ebaymotors/MINI-QUAD-ETON-KASEA-POLARIS-XTREME-54MM-RING-SET-/250556005177?pt=Motors_ATV_Parts_Accessories&hash=item3a564d3b39
Here too;
cgi.ebay.com/ebaymotors/KASEA-POLARIS-DINLI-ETON-54MM-RINGS-BIG-BORE-KIT-/170393796116?pt=Motors_ATV_Parts_Accessories&hash=item27ac42fe14

[90GTVert]

Thanks. I already had a piston kit on the way. Was planning to hone again. I'm just sad now cause I gotta wait. lol I wanted to do more wheelies.

[190mech]

While you are waiting,go ahead and build some wheelie bars!

[90GTVert]

lol That's no fun. ;D Although it would be funny to roll through town with a scoot and wheelie bars.

[190mech]

I had a thought,it'd be some extra work,but how bout if you install the 52mm ATV cyl while waiting for the 54 piston set?That way you'd know if the knock was from the jug or the crank and you could work out the other bugs in the mean time...

[2strokd]

Thats a good idea John!

[90GTVert]

I had the same thought last time I was messing with it, but I decided to wait. Don't wanna mess up any more gaskets than I have to and I might work on the SunL instead. Still got cleanup work to do to get all the sealant from the reeds off (threebond again lol) and little stuff like that. Piston kits shouldn't be long anyway I don't think. I ordered from PFS because they had a good price, I know they are reliable, and the Hoca 54mm piston measured the same from pin center to crown than the Koso piston does. I was thinking I'd install it and hope for the best, but if I still hear the noise I'll swap cylinders/pistons.

[90GTVert]

I got a little bit done last night, starting with honing the cylinder. As you can see, I still have teh scars from the initial crank failure on T2 though. I can't feel any of them, but theycan be clearly seen.



I got the piston kit in the other day.



I installed the piston and checked the port timings over and over as I filed it. I decided to try using just one base gasket this time to get a little tighter squish clearnace. I didn't really like the 140psi that I got with 2 base gaskets and a filed piston. Hopefully that will improve a little.



I ended up with 0.77mm of squish clearance, then added a thin copper gasket to make it 0.96mm. Kind of an odd squish shape, but from what I saw last time, it still works.



I did check the new piston in the cylinder with feeler guages. I came up with the same 0.0045" of clearance as I did with the old piston. If it wasn't an issue with worn rings, I'll probably be needing a new cylinder. I guess that shouldn't be too surprising after better than 7,000 hard miles and a crankshaft failure. Still, hopefully it'll work out this time.

EDIT : Forgot to mention, the port durations are 183 exhaust, 128 transfer. With 2 base I had 184/130. I could go farhter on the transfers, but I like to leave a bit of material above the ring lands and at least they will still just barely clear at BDC.

[2strokd]

Ahh thems just oil gallies in the cylinder now .
Looks good :thumb: !
I have been pretty happy with my Hoca stuff so far :clap:

[90GTVert]

Yeah I like it. The varis and rear pulleys are good. The piston seems as good as the Koso, but costs a little less. ;D It doesn't hurt that PFS is a reliable dealer carrying their stuff, so you know you won't get a raw deal that way either.

[190mech]

I always called those extra grooves transfer ports!

Edit,It'll be interesting if to see if performance is gained with the base gasket shuffle...

[2strokd]

I didnt know Koso made pistons???