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how do i tell whats been done to my banshee motor


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#1 mikey7o2

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Posted 16 October 2011 - 07:45 AM

Hi my name is mike i just bough a 1997 yamaha banshee. I can see that it has PTR pipes (im not sure if they are hi rev or mid range) and a PTR cool head , with a twin carb set up. It has a bad right cylinder and Im trying to figure out what all has been done to the motor. The previous owner has no idea what was done to it, becuase it scared her and then her friend blew it up (Im going off what she said). I plan on building it for trail ridding but I want to know what all was done to the motor, is there any way I can tell what was done to it? I will be doing the work my self and I have the skills needed to do so (I have about 15 years building cars under my belt) but dont really know what to look for. Any help would be great !!!

#2 Jereme6655

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Posted 16 October 2011 - 08:03 AM

gonna have to pull the motor down to tell really. if you say its got a bad right cylinder then your probably planning on pullin the jugs anyways. BUT FIRST (if you haven't already) do a compression test (WOT and kick til the needle stops moving) and a leak down test (instructions to build one are in the general section i believe) to see where your at. Chances are it may have gotten an air leak and melted a piston.

To check for port work your gonna need to pull the jugs off and look at the intakes AND the exhaust side to see if they've been ground on.... pay attention to the transfer support.....if its square on the front then its usually gonna be stock....if its got a knife edge on the front then its been ground on for port work.

You can either measure the stroke of the crank by measuring the distance from TDC to BDC... and also you can measure the distance from the center of the big end of the crank to the center of the little end to tell if you have a stock length crank or a +5 crank (helps with side load on the piston with the longer rod)

also when you get your pistons out see if you can remove some of the carbon on top and look to see if there are any numbers on the domes......if they've been replaced and replaced with wisecos then the number will either start with a 513 (stock piston) or a 795 series piston.

also post up some photos of your bike and we can tell you more about it from the photos......make sure you get photos of the bike to us too.

#3 spurdy

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Posted 16 October 2011 - 08:13 AM

Hi my name is mike i just bough a 1997 yamaha banshee. I can see that it has PTR pipes (im not sure if they are hi rev or mid range) and a PTR cool head , with a twin carb set up. It has a bad right cylinder and Im trying to figure out what all has been done to the motor. The previous owner has no idea what was done to it, becuase it scared her and then her friend blew it up (Im going off what she said). I plan on building it for trail ridding but I want to know what all was done to the motor, is there any way I can tell what was done to it? I will be doing the work my self and I have the skills needed to do so (I have about 15 years building cars under my belt) but dont really know what to look for. Any help would be great !!!



You will need to measure the stroke length to tell if it is stock or not. 54mm stroke is stock. Measure the bore diameter to see how much life is left on your cylinders, 64mm is stock. 66mm is as far as most anyone here would tell you to go safely. To check for port work you can easily tell if the casting flaws have been removed from the intake and transfers, polished exaust ports, but to tell what type of porting has been done you will need to measure the intake, transfer, and exhaust port heights, size and shape of them as well. Usually a builder can tell you how the motor will react with this information. To tell what has been done to the tranny would require splitting the cases. I am guessing that if the owner didn't know what was done, there is likely nothing done to the tranny other than maybe minimal some clutch stuff.

I would also pressure test the cases/top end to see if there is an air leak. You want to know what happeded to the cylinder that is bad. You can tell a lot by what the piston and dome look like. A compression test at this point is useless. Do a compression test after you get it rebuilt so you have a baseline for when the top end needs to be freshened up next time around.


SP

#4 Jereme6655

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Posted 16 October 2011 - 08:37 AM

my idea about usign the compression test at this point is cause the previous owner didn't know a thing about the bike......so maybe it was something stupid and simple like the right side munched a reed and that's why the right side wont fire haha......hey it could happen lol

#5 mikey7o2

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Posted 16 October 2011 - 08:50 AM

Wow thanks !! I honestly didnt think I would get such detaled info ! I do know that the right cylinder head i pitted BAD!!!!! It almost looks like a piston ring went bad and spent some time in the chamber getting smashed against the top of the cylinder. I did do a " getto" compression test buy putting my thum over the spark plug hole and kicked it about 5 times and I could feel a little pressure. I will run a real test and get the results posted as well as some detaled pics. Again thank you for replying to my post! I have always wanted to build a banshee and it does look like it has some money into it I just want to make sure I know what was do so when I get deep into it I know where my starting point is .

#6 mikey7o2

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Posted 16 October 2011 - 08:53 AM

You will need to measure the stroke length to tell if it is stock or not. 54mm stroke is stock. Measure the bore diameter to see how much life is left on your cylinders, 64mm is stock. 66mm is as far as most anyone here would tell you to go safely. To check for port work you can easily tell if the casting flaws have been removed from the intake and transfers, polished exaust ports, but to tell what type of porting has been done you will need to measure the intake, transfer, and exhaust port heights, size and shape of them as well. Usually a builder can tell you how the motor will react with this information. To tell what has been done to the tranny would require splitting the cases. I am guessing that if the owner didn't know what was done, there is likely nothing done to the tranny other than maybe minimal some clutch stuff.

I would also pressure test the cases/top end to see if there is an air leak. You want to know what happeded to the cylinder that is bad. You can tell a lot by what the piston and dome look like. A compression test at this point is useless. Do a compression test after you get it rebuilt so you have a baseline for when the top end needs to be freshened up next time around.


SP



What is the best way to do a pressure test on the top end ? Or would it be better to just take the top end to a shop and let them run that test?

#7 kodie

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Posted 16 October 2011 - 09:54 AM

For pressure test (leak down test) there is a thread at the top of the general banshee topic that will tell you how to build a leak down tester for cheap and effective. But saying that your head is pitted on the bad side of the banshee then I would say your piston is shot and your cylinder has some scarring and scratches on it. Get some pictures of what ever you have a question about get a picture of what you want to know about and we can help.

#8 spurdy

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Posted 16 October 2011 - 10:06 AM

What is the best way to do a pressure test on the top end ? Or would it be better to just take the top end to a shop and let them run that test?


X2 on the pressure test. The pitting can be cause from numerouse things. Typically any debri wont spend much time in the chamber. Most things flow out through the exhaust quickly. Pitting can also be caused by detonation. However, there is a distinct difference in what mechanical pitting and detonation pitting look like. If it got too hot you will likely have scarring on the piston and cylinder wall. The area this occurs in will tell you a lot about the failure as well. Don't let a shop pressure test for you. IMO don't let a shop do anything for you. The motor needs to be fully assembled to test anyway. It doesn't have3 to be in the frame but the cyls and the head need to be on.

SP

#9 mikey7o2

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Posted 16 October 2011 - 10:13 AM

Ok this is great !! I dont like any one working on anything I own so that was a great link for a pressure tester. I plan on getting back to work on the banshee in about an hour and will take some pics and post them. I know alot about high reving motors (thanks to the honda b series) and I know will catch on quick with a little help thanks again. Ill have pics posted later today.

#10 volcrano

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Posted 16 October 2011 - 01:52 PM

definately compression test.also the pitting on the head could have been caused by a previous failure.minor pitting is ok and runable.the leakdown kit will cost about $20 to make.it should hold 6 psi for 6 mins.1 psi per minute is acceptable but no more or u have a leak.

#11 spurdy

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Posted 16 October 2011 - 09:47 PM

definately compression test.also the pitting on the head could have been caused by a previous failure.minor pitting is ok and runable.the leakdown kit will cost about $20 to make.it should hold 6 psi for 6 mins.1 psi per minute is acceptable but no more or u have a leak.



Um....6 psi for 6 mins or it can leak 6 psi in 6 minutes? This is what you have if it leaks 1 psi each minute of the 6 minute test which you just said was acceptable :shootself: , 0 psi after your 6 minute test. Epic failure! If you leak 1 psi after during the 6 minute test you have a leak.

None of my motors leave the bench until they hold 6 psi for 6 minutes. It isn't going in my frame until it is right. 1 psi leak in 6 minutes is too much. If it leaks that much the leak will only get bigger. It's just an air leak, find it, fix it, ride hard with the peace of mind that you're running a solid motor. It isn't that hard to build an engine that doesn't leak.

Just my 2 cents.

SP

#12 mikey7o2

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Posted 17 October 2011 - 12:13 AM

ok so i just got home from tearing down the entire motor and getting all the part numbers off the crank, connecting rods, pistons, cylinders, and heads. it has a hot rods stock crank and connecting rods. paul turner heads with 17 domes (not sure what that means yet could use some help there) paul turner high rev pipes im not sure what type of cylinders it has but they have been ported and the part number is 347cm3 i think and i could use some help with what type of pistons it has i found what i think is a part number on top of the pistons its 58436 and it also has a twin set of kehin carbs part number 295bonjm if u can help me figure out just what was done to the motor it would be a big help. im going to rebuild the motor because when i pulled the number 2 cylinder off the piston was f#%ked !!

#13 Jereme6655

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Posted 17 October 2011 - 05:31 AM

ok so i just got home from tearing down the entire motor and getting all the part numbers off the crank, connecting rods, pistons, cylinders, and heads. it has a hot rods stock crank and connecting rods. paul turner heads with 17 domes (not sure what that means yet could use some help there) paul turner high rev pipes im not sure what type of cylinders it has but they have been ported and the part number is 347cm3 i think and i could use some help with what type of pistons it has i found what i think is a part number on top of the pistons its 58436 and it also has a twin set of kehin carbs part number 295bonjm if u can help me figure out just what was done to the motor it would be a big help. im going to rebuild the motor because when i pulled the number 2 cylinder off the piston was f#%ked !!


you my friend....have found a motor that has definately got some mods done to it.

17cc domes means the dome (stock is like 23-24) is now 17cc's. basically it seems (depending on your elevation) that your motor was set for race gas. the 347cm3 that is on the side of the cylinders is the actual displacement of the cylinders........they're stock jugs......347 cubic centimeters.... aka a 350cc motor lol. my opinion is to send your cylinders to a site sponsor on here to get em bored and honed and new pistons......ask them to check out the port work and give their ideas about it. They will be able to tell you whether its a dune/play port or a drag port etc,etc.....and they will have the means to get you the correct pistons (and at the best price) for your application.

My choice is Jeff at FAST. But i do know that Kevin at HJR also does some great work.

#14 mikey7o2

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Posted 17 October 2011 - 07:23 AM

you my friend....have found a motor that has definately got some mods done to it.

17cc domes means the dome (stock is like 23-24) is now 17cc's. basically it seems (depending on your elevation) that your motor was set for race gas. the 347cm3 that is on the side of the cylinders is the actual displacement of the cylinders........they're stock jugs......347 cubic centimeters.... aka a 350cc motor lol. my opinion is to send your cylinders to a site sponsor on here to get em bored and honed and new pistons......ask them to check out the port work and give their ideas about it. They will be able to tell you whether its a dune/play port or a drag port etc,etc.....and they will have the means to get you the correct pistons (and at the best price) for your application.

My choice is Jeff at FAST. But i do know that Kevin at HJR also does some great work.



well im in las vegas and the elevation hear is right about 2001 ft how but from what the person i bought the quad from said it came from cali just not sure where in cali !