What compression???

[badquad]

My son has a stock motor on his Banshee, and he was having trouble getting it started. It has gas, spark and air, and the throttle cable is fine for TORS, so we were thinking that his compression is getting low. Its a 2004 on the stock motor.

What should a banshee's compression be?
How should it be checked? 1 plug in, compression checker in the other plug hole, open throttle, air filter off, both plugs out? I am not sure what the procedure is for the banshee. Any help would be appreciated.

Thanks.

[Dinner]

Stock Compression should be around 110-125ish depending on where you are. Each cylinder should also be pretty close to each other in pressure as well.

Easiest way is leave one plug in, and have the compression gauge in the other. Hold the throttle wide open (you can leave the air filter on) and keep kicking until the needle stops moving in the gauge. Remember this pressure, then switch the gauge over to the other cylinder (remembering to put a spark plug in the cylinder you just did). Again, keep kicking until the needle stops and see that pressure. Both should be close/the same as each other.

Let us know what pressure you find. Anything below 105, in my opinion should get at least new rings and see if that helps. If not then you can consider a hone/piston upgrade.

[1banshee]

A LOT OF TIMES IF A BANSHEE BREAKS OR EVEN CRACKS A REED IT WILL LOOSE COMPRESSION THROUGH THE INTAKE SO CHECK YOUR REEDS. IF THEY ARE REAL WET START LOOKING CLOSER CHANCHES ARE THERE BROKE OR CRACKED ON ONE SIDE.

[Hondamaster5505]

the wear limit for banshees is 100psi i think.

We've had out banshee down to like 80psi one time, with shaved heads:eek:

When we rebuilt it, it was running about 135, so im guessing with an untouched head, it should be around 115-125

[badquad]

Thank you all for the feedback. We went to test it, and kicked about 12 times and it only got up around 100 psi. Both sides were the same. Could that be possible, that both sides are worn the same, so the compression is the same. Sounds kinda weird to me,, maybe I need to check my connections on the compression tester, and I will check the reeds also.. Any other suggestions before tearing it apart..

Thanks

[Hondamaster5505]

well, 100 is the wear limit, we've ran it past there though.

I say rebuild her with .10 or .20 over high-compression pistons.

It'll run strong, and be a little faster.

And a side note, be careful who you send the cylinders out to to be bored. There was a local machinist who said he did them before and his customers are happy, so we sent them to him. When we got the cylinders back, the were BUTCHERED.

So we went to my dads shop, and honed them a bit thinking they might have a chance at surviving. He measured the bore and they were a little over-sized, but he thought it might work for the weekend.

We went home, and rebuilt the shee. And it was running lower compression then before he tore it down!!!! It was running around 70psi with a milled head..

So we ended up having to take it to someone else and bore it to .30 over :grr:

When he had them off, he measured them better, and it ends up they werent even, and had a taper in the middle. This is when he still had them from the other guy who butchered them. They were a million times better when we bored it to .30 over

So the moral of the story, BEWARE OF WHO YOU TAKE THEM TOO!

lol

[bloodmoney23]

well regardless i would buy aftermarket reeds. The hold up better and have a better air flow. The stock ones place to much restriction on the bike. You should be able to get away with just a hone as well and pick up some stock bore pistons. A machinist will let you know wether they need bored or not. My best guess for ya is that the rings are just worn and possibly gaskets are starting to leak. They will eventually do that any point after a full year. Anyway good luck with the bike.

[Dinner]

If the gaskets are OK you can re-use them. But if you are iffy then get new ones. I have had my cylinders off and on enough times to do my own clean up porting and they haven't leaked yet.

Having the same compression in each cylinder is usually a good thing. Shows that the cylinders and rings are wearing evenly with each other and that your cylinders are generally getting the same amount of air/fuel mixture.

100Psi is getting pretty close to a re-build and yes as the compression drops it will be harder to start. If you want, you can at least check your cylinder walls and see if they are in good shape or not. If they are, put a new set of rings in and see if that helps. The only thing is that you have to run the bike for a bit until you seat the new rings. And so if it ends up being that you do need a bore, new piston and rings, then you have to take the bike apart again.

So it's pretty much up to you. Put in new rings and be on your way. have it honed and put in new rings and or pistons. Or have it bored and have new pistons and rings put in.

[Washburn]

You might be getting a low reading because your not useing an adaptor on your comp reader. Mine came with 2 adaptors a 14mm perfect and an 18mm too long would hit when piston hit TDC. You should have about the same length adaptor as the spark plug.

If it got colder where you are you might need to rejet. That can be a problem as far as starting it up and getting the proper air/fuel ratio.

[badquad]

Thanks for all the feedback. We are going to take the head off tonight, and see what he cylinders look like. If they look good we might just go with Piston and rings, but if they need to be honed, or bored my son is going to wait unitl he can save more money and get some work done to it.
Again thanks.