pittss1c

The deformations in the bore are not very sharp, so it looks like I can measure them relatively accurately at ~.127mm, so that means you would have to bore a little over .25mm to get it round. I hope this means that a bore from +1.5 to +2.0 should be a piece of cake... Now I just need to pick a shop. I see FAST advertises here. Are they the best solution?

Has anyone ever measured their piston after it has been used? I just had a cylinder failure that looks a lot like the ring caught the exhaust port. For fun, I measured the cylinder and piston... then called the piston manufacture to find out the sizes of a new one. The jug is dead on at .060 over (1.5 mm)and the piston has 1.5 marked on the top....sounds good! But when I measure the piston, (10 mm above the base) it is ~1.25 over. Actually, I had the piston manufacturer measure a new +1.5 piston and it seemed all the dimensions of the piston I have (also marked 1.50) were about .25 smaller than a new one. Do pistons change sizes this much, or do you think the guy who put the engine together got bad pistons? I realize that this is still an indication of a bad engine builder. Amazing that the skirt didn't break first! I can actually move the piston around in the cylinder noticeably in the non-failed cylinder. I am assuming now that this is the cause of the ring getting caught, not due to incorrect chamfering.

I'll see you one cheap! (of course it has the same problem as yours) If you find one much under $40, post it here... That is about what I found when I looked.... robbery! Looks like sudco is 27.39. Still too much! Since I can't reach the choke on the right carb very well, I start it with choke on the left carb only, and I put the bad one on the right.

There seems to agreement that the ring caught the port. I assume this happens only because of a poor job in the port chamfering. Now I will be trying to find the right person to take the cylinders to.

The only markings on the top are 1.50 and an arrow. The inside of the piston has an HR on 1 side, and the other says S1 I believe. I assumed this is a hot rods piston. (should be a stroker model) that is +1.5. (I could measure the bore this weekend) So this should be .060 over (1.5mm/25.4mm/in)=.05900551....) There aren't tight scratches in the bore, but you can feel the deformation above the exhaust port with your finger.

Help me understand the math first... I have 1.50 pistons (65.5mm) isn't this 1.5mm over ~=.060 of an inch (not .100) Also, who then uses the other banshee pistons... 66.00,66.25,and 66.50 (or in my case with a long rod, the 66.00 pistons)?

this is the first tear down after I bought it, so I don't know 100% what I have. I expect to know everything by the time I am done though. It looks like the engine was pretty stock before he put the 4 mil in, so there is a good chance they are stock cylinders. Any guidance on how I could answer your question better would be welcome.

I have seen some posts that sounded like cylinders at 65.5 weren't worth boring or indicated that it was the last bore... I see Weisco makes pistons that go to 66.5, so what are they for then? I have some jugs with damage (no sharp scrapes, but I can feel deformation) and the pistons currently say 1.50 on them... I'd hate to have to start from scratch (since these are already ported for a 4 mil wit a long rod) What is the real story on how far to bore?

Don't know. I bought it freshly rebuilt. The pistons have 1.50 stamped on them... time to start figuring out where to get them reworked if they can be.

piston port damage port2 dome I have had some overheating issues, but I don't want to jump to any conclusions. I am actually a little concerned that the ports weren't done quite right. I probably obly have 10 or 15 good rides since the topend was redone. Any input is appreciated.

Not good! My teardown/inspection did not go well. I need to do a topend. won't happen by the 10th. May still come, but no banshee.

T_shee... I'm here, just been really busy lately. I am planning on coming, but may bring some people. I owe someone a ride. I traded some babysitting for 4 wheeling. I need to tap into my shee though. I have reduced compression on one side. Should be able to get it worked out by the 10th though. Either way I will likely bring my blaster and an rm250 as well.

I am in the same boat as you. Moving down the road, it cools OK. (180-190) Get into the tight woods with hills, and I am screwed. It can hit 235 quick. and it doesn't necessarily boil over. I have a trailtech, and I have seen peaks higher than that. I am seriously considering installing a fan.

I wouldn't say we have "no" business in Iraq. We now have a military force and bases along an immediate border with Iran. Is it worth it for just that... of course not, but it is a valuable perk. It is hard to find a friend in that region to base military operations.... Saudis are not our real allies nor is Pakistan. Maybe they figured we could "make" a friendly nation.

Wow! no response? I guess I am going to scrap the trip for this weekend and try another time.

I am trying to get my banshee back together for the ride... everything is on schedule, but if no one is going to BL, I'll go somewhere else... The weather was fine today and is scheduled to be sunny tomorrow, but they are planning on showers on Friday! How many are still in?

This should be interesting. That is customer appreciation day. Free food, prizes and fireworks. There is a TREC race at night.

I bought an old dirt bike, and the manual says new piston and rings every 6 hrs or 3 races. That is for a stock bike...Ouch! So, 45 hrs on a banshee should be considered good I guess. (though it might not feel like it)

Some guy with stock geating and 18" tires.... You know they are full of crap about that, what else are they...

I looked up that calc before I posted... The time I made the run, I had 4000ft of smooth concrete. the gearing was 14/42. So, if the GPS was correct (and I can be pretty sure it was) then either the tires are bigger then I think at that speed or the RPM was higher than 10,500. (which would agree with the trailtech) I of course believe you 100% that the engine doesn't make any power past 10,500. That is what makes me wonder how hard it is with big tires and 15/40 or 16/40. My mods aren't too extensive 4mil stroker long rod, PWK28/pods, at the time - DG exhaust, and as for porting, the guy I bought it from had it done and only referrered to it as "mild" (maybe just to acomidate the crank/rod) and low compression/pump gas. I have read enough posts that, if you (dajogejr) say it is harder then it sounds, then I do believe you.

You know, I am tempted to gear mine to go 101 MPH and post it here just for the flame wars. My quad isn't insane or anything, but with just going up a tooth on the front sprocket, I got to 93, and the engine was way past the power band. I am not sure what RPM I was at when I hit top speed, but my trailtech said my tach peaked at 11,300 or 11,500 (don't remember) So, I am not convinced it would be that hard to beat 100 mph. am I missing something?

Fast banshee try that

it must be true.... Hell, it was GPS radared.

I also would like to disagree. I have a very similar setup (except pipes) Due to some mistakes on my part, I have been pretty far off from time to time on my jetting in both mains and pilots. (too rich always) And I actually have never had a bog. (I have fouled plugs and lost power) So unless maybe you have the wrong needle or something (I never tried that) I don't see how one could say you can't get rid of bogs with those carbs. Will all my errors, I have failed to even create a bog. Mike

I will actually try to be helpful... The answers are correct here regarding the efficient range that the engine operates in. The reason that it is discussed here so much (and with 2 strokes in general) is that a 2 stroke has a lot of rpm range with inefficient operation. There is a user here with a cool profile picture that shows a a 2 stroke operating in an efficient RPM range. It shows the the cylinder being over filled with air/fuel mixture to the point it flows well into the exhaust. Then after the intake port has been covered by the rising piston, but before the top of the exhaust port has been blocked by the piston, a returning pressure wave due to the constriction of the exhaust pipe near the end pushes the air/fuel laden exhaust back into the cylinder before the piston has risen high enough to seal off the exhaust port. The effect is that you get a lot more fuel/air into the cylinder then the displacement of the engine. (which equals more power) The problem is that the returning pressure wave is time dependent (different length and shape pipes change the time it takes the pressure wave to return). So if the engine is turning too slow or too fast, the extra fuel/air does not effectively get stuffed into the cylinder. (some people call this effect of the 2 stroke power band "being on the pipe") It is an important part of the power band of a 2 stroke and part of why it is so much more prominent and sometimes sudden.