No powerband

[Jbducati]

Hey guys I got this blaster cheap with a hole infront of the engines sprocket. I've fixed that and it's not leaking. But it won't hit power band or hit high revs like it's suppose to ever once in a while it will blip into it like a surge. It really just bogs from about three quarter to wide open. It looks like someone ported it but it idles awesome and the low end is awesome I have a uni filter right on the back of the carb with a vitos pilot jet and needle stock 230 main jet and on the leanest (top) groove of the needle. That's where it runs best which sucks. Plus the plug is black. Any ideas? Reeds? Vacuum leak?

-John-

 

[acezeesawtooth]

first off do a leakdown test and a compression test. if those two come back clean perform a plug chop... but before you start it again raise that main jet up to id say a 250 or 260 if its "ported" you are running way lean.

 

[gearhead04]

for starters you main jet is too small with any kind of aftermarket filter

 

[Larry's Shee]

Air filter clean? Carb? Float level good? What kind of oil? Ratio?

 

[super noober]

check the reeeeeeeeeeds

 

[Blaner]

check the reeeeeeeeeeds

check the reeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeds

i agree that that is WAY to lean, richen up! and do a comp test and a leaktest, those are the starting points of any engine diagnosis.

http://www.blasterforum.com/do-yourself-20/build-use-leakdown-tester-10663/ you can also buy leaktetsers from dudes on the forum such as slickerthanyou

 

[sicivicdude]

If everything else is working correctly, the clip on the needle should be in the middle position (number 3) and the main jet should need to be about a 290-300 depending on your elevation.

It sounds like you're still WAY rich even with stock jet and the needle at the leanest position so let's start with some basics.

Download the service manual from the "general support" section of this forum. There is an ignition troubleshooting section in there which will help you make sure you don't have a dying ignition component.

You also need to do a compression test (abnormally low compression will make your jetting SEEM rich) and a leak down test to confirm the internal health of the engine. Any problems with the internal health of the engine need to be corrected BEFORE worrying with jetting.

Once you've got the engine healthy, you need to remove the carburetor and clean it thoroughly making sure to check the float height (too high could cause flooding which will mimic your problem) and clean all of the air bleed holes coming from the air filter side of the carburetor into the throat.

You should also consider putting a velocity stack back on your carburetor, a pod air filter has a tendency to allow turbulence to bypass the bleed holes which CAN make your jetting super rich (or at least erratic). Either the stock air filter assembly or at LEAST a short piece of pipe between the carburetor and filter.

There is one more thing to be on the lookout for and this is some ODD-BALL stuff right here. I ran into the strange coincidence that I KNEW a motor was good (I had been running it before my buddy got it) but it wouldn't run worth a DARN. Spitting and sputtering and generally acting VERY poorly. So I tore into the carburetor (which had an unknown history) like 5 times. I pulled the float to make sure it hadn't saturated, I pulled the needle out and changed it, I tried tubes on the outside of the carb, I tried everything. The best way it would run is similar to your setup (actually my buddy installed a 200 main jet and had the clip position at the top) and I FINALLY found the problem.... the carburetor had been generously donated by a BF member with a totally unknown history. Apparently the person who had it before had done a little monkeying with it... they had installed a banshee right side carb slide into a left side carb.... the slide really didn't catch my eye because it looked right at a glance. It wasn't until I was really paying attention to the slide height (to set the idle height)that I noticed the cutaway was backwards! Instead of creating a venturi to pull fuel up the needle, it was creating a suction on the needle the whole time and sucking gasoline down. It was actually spewing enough gasoline out the tailpipe it soaked the silencer and then caught it on fire one time! Just goes to show you just never know...

 

[Jbducati]

Thanks guys I'll do that compression and leak down test. I'm runnin 32:1 gas oil ratio I just don't under stand why the plug is black. And when I check the reeds I'm checking for gap and a crack or something right.

-John-

 

[sicivicdude]

You're looking for cracks, missing chunks, or the reeds bent back up away from sealing.

If they're warped, SOMETIMES you can remove the mounting screws and flip them over to reuse them for a term. Eventually they'll need to be replaced... but you can get a few more turns out of them that way.

Reeds not sealing (for any reason) CAN richen up the mixture because it allows the engine to blow already fuel laden air back into the carburetor through the venturi again (to pick up more fuel) and then sucks it back into the engine through the venturi AGAIN (to pick up even MORE fuel). It doesn't take but a little hole in one corner of one reed pedal to allow enough fuel to flood your engine.

 

[Blaner]

good info AS USUAL from Sic, i would agree that the intake from the airbox helps with improving airspeed, that would make it richer without it.

these motors are pretty simple, its just a process of elimination

 

[Jbducati]

The float height was about .010 high and I put a 300 main jet in with a new plug and she runs strong. I also put a piece of pipe in-between the filter and carb. The engine made 175 psi so I'd say the top end is good.

 

[1995blaster]

wow thats a lot of compression. is your gage right? if its been ported it possibly could have a milled head. if you ever pull the head off take a look and see.

 

[alex90]

buy one of those green powerbands, way better than the stock blue ones

 

[Jbducati]

Yes the head has been milled quite sh*ttly. The guy must had tried lapping it with a lot of sand paper. And I perfer a red(ducati) power band but the blue will work for now haha. Thanks for the help guys.