b.rich108 Posted January 5, 2014 Report Share Posted January 5, 2014 Ok I have a handful of questions 1) My bike is bored .40 over and it has 21cc domes in a modquad cool head. What should the compression be at? Also, would 93 pump gas be ok with 21cc domes? 2) Would a stock bore have the same compression with 21cc domes as a .40 over bored cylinder would with 21cc domes? 3) My impeller drive gear pretty much blew up and I was wondering why it was plastic? Does anyone replace them with metal gears, or is it plastic for a reason? 4) I need new domes, and a lot of them say standard bore. Does that mean I need bigger domes because my cylinder is .40 over? Quote Link to comment Share on other sites More sharing options...
b.rich108 Posted January 5, 2014 Author Report Share Posted January 5, 2014 Also, what gaskets will I need to put the head back on? Quote Link to comment Share on other sites More sharing options...
b.rich108 Posted January 5, 2014 Author Report Share Posted January 5, 2014 All of the o ring kits for the modquad head look like they don't come with a main o ring to go around the whole head. Is that ring not needed? Quote Link to comment Share on other sites More sharing options...
vulvafan537240 Posted January 5, 2014 Report Share Posted January 5, 2014 1.) What's your elevation? 2.) See above 3.) There are aftermarket aluminum impellers. Buy one from a site sponsor. 4.) Std bore is fine for you. Big bore is considered 68mm+. O ring kits should have all the o rings including the big one. Quote Link to comment Share on other sites More sharing options...
dave5.0 Posted January 5, 2014 Report Share Posted January 5, 2014 Don't care about the other crap, sorry. But the drive gear is plastic stock. I'm not sure there are a bunch of sponsors carrying metal ones. I think Mull Engineering may make one. Not sure if anybody else does. Buncha companies make aluminum replacement impellers. That's the other end than what it sounds like you're talking about though. Quote Link to comment Share on other sites More sharing options...
Zillaguy Posted January 5, 2014 Report Share Posted January 5, 2014 1) Mull Engineering makes a billet aluminum gear for the W/P... I have one they work well.... 2) 68mm is considered big bore, any bore size up to 68mm uses standard bore domes. 3) .040 over is not going to effect compression... That is going to be determined by dome size, porting, and elevation. 4) 20cc is about as small as i'd go trying to run pump fuel safely... 5) Yes the big o-ring comes in the kit for the head.. Quote Link to comment Share on other sites More sharing options...
b.rich108 Posted January 5, 2014 Author Report Share Posted January 5, 2014 Thanks guys for answering my questions. I have a billet impeller already, I am talking about the water pump drive gear. I am only about 40' above sea level and I only got 120psi in the one cylinder. I never got a chance to check the other because the threads were all stripped out. I will be getting new domes shortly. I don't believe anything was ported in the motor. At least I was never told it was. I just picked up this bike and it is my first banshee. I was told it was just rebuilt, but I'm guessing if it is only Making 120psi when it should be making 155 that it's been a while since it was rebuilt. Also, does that mean it's do for a rebuild? Quote Link to comment Share on other sites More sharing options...
Zillaguy Posted January 5, 2014 Report Share Posted January 5, 2014 Take it apart and check your clearances... Asking us isn't going to tell you anything.... It needs to be disassembled and inspected/measured. Quote Link to comment Share on other sites More sharing options...
b.rich108 Posted January 5, 2014 Author Report Share Posted January 5, 2014 I am asking you these questions so I can learn what these things are supposed to be at. If everything is where it should be, there is no reason to disassemble. But I don't know what everything is supposed to be at, which is why I am asking. I have no problem with taking it apart and checking everything, but It doesn't make sense to do that if there are no issues. Quote Link to comment Share on other sites More sharing options...
dozer Posted January 5, 2014 Report Share Posted January 5, 2014 All of the o ring kits for the modquad head look like they don't come with a main o ring to go around the whole head. Is that ring not needed? that large oring is probably folded in the pics making it look half its size. we can tell you where everything should be so you have the info but without taking it apart you dont know if everything is where it should be or not. i believe mull engineering makes a metal drive gear but i have yet to have a plastic gear fail. small bore domes work for piston 64mm to 66mm i believe. Quote Link to comment Share on other sites More sharing options...
dozer Posted January 5, 2014 Report Share Posted January 5, 2014 also cranking compression gets lower the higher the exhaust ports are raised. so if your cylinders are ported, keep that in mind Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted January 6, 2014 Report Share Posted January 6, 2014 are you doing the compression test correct? install compression gauge, hold throttle open all the way and kick the motor over UNTIL THE NEEDLE STOPS MOVING.....none of that 3 kick crap. ALSO.....you need to ensure you're using a QUALITY compression tester AND the end of it needs to be the same length in the threads as the spark plugs or else it will throw off your readings. Report back.........the less you report back in here.....the less us guy who have been around are willing to help. Quote Link to comment Share on other sites More sharing options...
b.rich108 Posted January 6, 2014 Author Report Share Posted January 6, 2014 The one thing I did not do was make sure the end was in the same depth as the spark plug. I kicked it over a solid 15-20 kicks and the needle did stop moving. The compression tester I have was about $45. I am going to barrow my buddies who is a mechanic and has all Snap-On stuff. I will be sure to measure how far in to take it. Also, I have to look up what a ported cylinder looks like. I did not have it ported and as far as I know it was not, but I will check that too. I probably wont be able to work on it this week but I will definitely be at it this weekend. Thanks for the help. Quote Link to comment Share on other sites More sharing options...
b.rich108 Posted January 8, 2014 Author Report Share Posted January 8, 2014 I am hoping when I did the compression test I didn't do something right. I will be sure to post more as soon as I find out Quote Link to comment Share on other sites More sharing options...
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