700vflash Posted December 22, 2010 Report Share Posted December 22, 2010 I just got my top end back together and the piston is not clearing! I used a wiseco prolite piston, cometic base gasket and a head milled 30 over. Tightened the cylinder head nuts down finger tight and everything cleared, torqued them down and now it doesn't! I don't understand why this combo isn't working. I need advice please! Quote Link to comment Share on other sites More sharing options...
700vflash Posted December 22, 2010 Author Report Share Posted December 22, 2010 I also noticed that the intake ports are not lining up. The ports in the piston are about 3/16 higher than the ports in the cylinder. I also changed the crank but it stayed stock. Quote Link to comment Share on other sites More sharing options...
bigblockbanshee Posted December 22, 2010 Report Share Posted December 22, 2010 I had the same problem with the ports not lining up with my 513s but everything else was ok. This was my first build so I just assumed that's how they were originally... Quote Link to comment Share on other sites More sharing options...
dirtydownunder Posted December 22, 2010 Report Share Posted December 22, 2010 i was gonna say, it could maybe be a long rod crank with short rod pistons, but i dont think you can get a long rod stock stroke. so your pistons are sticking out of the bores ? Quote Link to comment Share on other sites More sharing options...
Wicked ATV Posted December 22, 2010 Report Share Posted December 22, 2010 i was gonna say, it could maybe be a long rod crank with short rod pistons, but i dont think you can get a long rod stock stroke. so your pistons are sticking out of the bores ? sounds like your missing telling us something. every should be fine if stock. unless you bought a Long Rod hot rods crank. then that would throw you off. But you would have to see if the piston stick out of the top of the bores. if not...... Then check to make sure the pistons are not snag up in a port or something. if they didn't get chamfered you might be hanging up somewhere. Let us know all the Pieces you change to know were your missing something. also by any change did you machine the stock head and not re-step it? just throwing things out there Quote Link to comment Share on other sites More sharing options...
700vflash Posted December 22, 2010 Author Report Share Posted December 22, 2010 I had to do a complete rebuild due to a rod bearing. Got a welded crank and milled head from juggs racing. Pistons i received from the seller of the banshee and was told they were wiseco prolite's. The rim of the pistons do stick out the top of the cylinders about a 1/32 and it seems odd that the ports are not lining up. Quote Link to comment Share on other sites More sharing options...
700vflash Posted December 23, 2010 Author Report Share Posted December 23, 2010 Well I contacted the old banshee owner and he said the pistons were a vito's/wiseco piston. I have found topics about clearance issues with the vito's .80 and .100 pistons and the cometic base gaskets being about .30 thinner than oem gaskets. I read one topic were the guy was going to have the dome bored out to the size of the piston. I think I am going to start with a thicker cylinder base gasket and hope that takes care of it. But that still doesn't help the intake ports being 3/16th off, should I worry about it or what? Quote Link to comment Share on other sites More sharing options...
fastquad02blaster Posted December 23, 2010 Report Share Posted December 23, 2010 I had the same problem with the ports not lining up with my 513s but everything else was ok. This was my first build so I just assumed that's how they were originally... And your bike runs good? All the power it used to be? I'm new enough that, I'm not real sure on the problem. I would think that the ports are supposed to line up at some point in time throughout the stroke though. Somebody else could give you better advice than I could. Good luck with it. Hope you get it fixed and running soon. Quote Link to comment Share on other sites More sharing options...
700vflash Posted December 24, 2010 Author Report Share Posted December 24, 2010 sounds like your missing telling us something. every should be fine if stock. unless you bought a Long Rod hot rods crank. then that would throw you off. But you would have to see if the piston stick out of the top of the bores. if not...... Then check to make sure the pistons are not snag up in a port or something. if they didn't get chamfered you might be hanging up somewhere. Let us know all the Pieces you change to know were your missing something. also by any change did you machine the stock head and not re-step it? just throwing things out there Sorry, but what do you mean by re-stepping the stock head? Quote Link to comment Share on other sites More sharing options...
Wicked ATV Posted December 24, 2010 Report Share Posted December 24, 2010 Sorry, but what do you mean by re-stepping the stock head? Sounds like your on the right path. Makes sense if the bore is 66mm and your head is still stock then the Piston will hit the head. You have to remember stock head I think..... Measures 64.75-65mm? and now your pistons are 66mm so possible the head gasket is getting in between also if the head gasket is the smaller bore head gasket too. Just check if the gasket fit over the piston also or just measure it. So what you might have to do is machine the stock head to 66.50mm or 66.75 and get a larger head gasket. Some after market kits like cometic come already with a 66.50 head gasket if you re-quest it. I know this to be a common problems with guy blowing head gasket when they get into the larger size bores. They forget to machine the head as well. The step is what is from the surface of the head to were the angle of the dome starts. Usually you want around .026 step considering the gasket is .010 already. Thou the problem i also see you say the piston edge is about 1/32 which is about .031 now that's about what you would get if you had no base gasket. or.... if some one deck the cylinders at one time before then that can also be an issue. So.... another thing you can do is take a digital caliper and measure how tall the cylinders are. You should have about a .025 base gasket if you bought a std gasket kit. Now for the pistons not lining up it's typical. they never are dead straight on. also if some one has gone in there and mess with the intakes unless they match them. So don't worry to much about that . I just seen you posted some one deck the head .030? man... there you go. if the piston is sticking out .031 and deck .030 now you just lost .061 from stock. as well if they only fly cut the head more likely they never open the dome bores either. so... 1- Check how tall your cyinders are to make sure they are not Decked 2- Check the bore size of your head 3- Check how far actually the edge of the piston comes out of the top of the bore. You can even use a set of filler gauges to match them up on the edge if you don't have a dial indicator to help you find that. 4- Check the bore of your head gasket after these simple steps you'll see where you problem is. If you even supply this info to your guy machining the head he can help you out. Or as well If you need the machine work done i can supply you a head already cut ready to drop in. I'll just need to know If your Ported?if yes... measure me the height of the Exhaust port from the top of the cylinders. Measurement in mm or inches. to give me a reference how much i would guess to machine the head for you. Also What elevation and What type of fuel? Sorry to ask so many questions but this are just things that are needed to be check to avoid major damage. Quote Link to comment Share on other sites More sharing options...
700vflash Posted December 24, 2010 Author Report Share Posted December 24, 2010 Without the head gasket on, the pistons sticks out .030 above the cylinder. The gasket bore is 66.5mm and the head bore is 65mm. I have new thicker base gaskets on the way, not sure how much thicker. So I am going to wait until the new gaskets are installed and see what that does. Quote Link to comment Share on other sites More sharing options...
700vflash Posted December 26, 2010 Author Report Share Posted December 26, 2010 I was wondering if it would be worth the hassle to have the pistions port matched with the cylinders. It is about 3/16! I am waiting for parts to put the top end back together and just wondering if it is worth it. The cylinders are torqued down and I have to remove them to install the new thicker base gaskets. Quote Link to comment Share on other sites More sharing options...
bigblockbanshee Posted December 27, 2010 Report Share Posted December 27, 2010 And your bike runs good? All the power it used to be? I'm new enough that, I'm not real sure on the problem. I would think that the ports are supposed to line up at some point in time throughout the stroke though. Somebody else could give you better advice than I could. Good luck with it. Hope you get it fixed and running soon. Sorry I just saw that you quoted my post. I actually haven't started mine yet, it's about 90% done and sitting in the frame. I was just speaking from what I noticed after I assembled it so I have no idea if it runs good or not. Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted December 27, 2010 Report Share Posted December 27, 2010 I belive allout drag racers port match the piston but be aware it affects reliability considerably (weakens piston) Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.