ma scoot has the sputters! NH80 problems

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b1jackson
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ma scoot has the sputters! NH80 problems

Post by b1jackson »

So I am a bit stumped at whats going on. The 85 Aero I bought was sitting for a couple of years. It ran but not that great. Seemed a bit boggy on the throttle and was unresponsive. Here is what I've done to try to fix the boggy and irratic power:

- tank completely off, flushed twice, fresh gas with a bit of seafoam.
- carb taken apart twice, all cleaned out, larger main jet put in, blown clear with air compressor and re-installed
- put an in-line fuel filter in just in case
- changed fuel line and a couple of vacuum lines that were cracked looking.

The damn thing is still bogging out. It seemed when I put a good dose of seafoam in the tank, it ran pretty good. Took it down the road and it hit 40mph and seemed totally responsive to throttle twists. It didn't pull me off the handle bars or anything but was definitely running better. Ran out of gas. Then pushed it home. Put more gas in it..took it for another rip and the same bloody thing. On the road its boggy, kind of sputtering (like a plugged fuel filter..sort of surging a bit) and working the throttle back and forth abit just makes it bog out and cough.

Any ideas? The carb is totally spotless with the brand new larger main jet. There also is a brand new plug in it. I am not sure the brand or type of plug. It was in the glovebox of the scoot when I got it and still in the package so I put it in to try.

What are the symptoms of a plugged muffler? Getting frustrated cause I am pretty sure its something simple but I've covered all the simple stuff I can think of?
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Re: ma scoot has the sputters! NH80 problems

Post by Bear 45/70 »

First off the rule is "DO NOT RUN OUT OF GAS!" It leans the hell out of your motor. How big a jet did you put into the carb to replace the stock one? Compression check? Is the airbox and air filter in place and is the filter in good shape and oiled properly?
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Re: ma scoot has the sputters! NH80 problems

Post by b1jackson »

jet is a 90 as per your recommendation. Air filter and airbox all in tact, air filter all washed out and oiled too.
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Re: ma scoot has the sputters! NH80 problems

Post by Dan Durston »

I've only had a plugged muffler once (on a CV80) and the scooter simply ran extremely slow. Top speed was like 25mph which rose to about 36mph with a new muffler.

Have you done a really good check for any air leaks in the intake area?
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Re: ma scoot has the sputters! NH80 problems

Post by b1jackson »

yes. With it running, I've cupped my hand around the intake and air box area. The intake bolts are tight into the carb. Good snug fit and all o-rings in place. All hoses good. The air box into carb rubber is in good shape and tight as well. What confused me was why it seemed to run so well with seafoam in it? Then take that out of the tank (or dilute it with more gas) and the bogs come back?

Speaking of the carb, there is a hose on the inner side of the carb that is just open and unconnected. Its a short elbow piece bent on a 90 degree angle which I am assuming is just some sort of vent hose. I see nowhere to connect it and it looks factory.

I'm going to pick up a compression tester and see where that leads me. I need one anyway to add to my tool collection.

The muffler has had surgery on it before. When I had it removed to paint it, you could see the weld scars where someone had it opened up. If the compression test comes out OK, I think that I am going to do the brake cleaner/oven cleaner soak job to the muffler to eliminate that possible problem.
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Re: ma scoot has the sputters! NH80 problems

Post by Bear 45/70 »

Change the spark plug. Go with a BPR7HS or even a BPR8HS.
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Re: ma scoot has the sputters! NH80 problems

Post by b1jackson »

Crap. Compression test got me around 80 psi. A bit of Lucas oil supplement in the cylinder gained me a bit but not much. Looks like a top end rebuild! At least I'll have online company.

I'll have to think about this. I may just sell it as is and let it be someone elses tinkering project. It is a pretty comfortable little scoot though. Ahhh decisions.

Can anyone give an opinion as to why it seemed to run and have decent power with the seafoam mixed in? Was it like some high octane jet fuel or what? Maybe I could just run it with a seafoam bottle set up like a NOS tank with a nozzle injection! :shock: :lol:
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Re: ma scoot has the sputters! NH80 problems

Post by Bear 45/70 »

b1jackson wrote:Crap. Compression test got me around 80 psi. A bit of Lucas oil supplement in the cylinder gained me a bit but not much. Looks like a top end rebuild! At least I'll have online company.

I'll have to think about this. I may just sell it as is and let it be someone elses tinkering project. It is a pretty comfortable little scoot though. Ahhh decisions.

Can anyone give an opinion as to why it seemed to run and have decent power with the seafoam mixed in? Was it like some high octane jet fuel or what? Maybe I could just run it with a seafoam bottle set up like a NOS tank with a nozzle injection! :shock: :lol:
There is alcohol in Seafoam but I doubt it hops the gas up, besides high octane gas has no more energy per gallon than regular. The octane lets you run higher compression but the extra power is from the compression, not the energy in the gas.
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Re: ma scoot has the sputters! NH80 problems

Post by b1jackson »

Well since everything was all cleaned up on the bike and it was on the stand, I may as well get at it and see how it looks from the inside out. Had to take off a few more bits and pieces than expected (like the floorboard and left side running board) but overall, an easy job.

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The piston and rings will be replaced but I lucked out on my cylinder wall. I gave it a quick honing with a honing tool and its groove and scuff free. So looks like I'll order some parts and I hopefully will be good to go. That stand I made for working on my scoots was time well spent. Better working at eye level where you can see things rather than bent over or crawling around on the floor!
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Re: ma scoot has the sputters! NH80 problems

Post by Bear 45/70 »

You did luck out, from the looks of those rings you should have had some pretty good grooves in the cylinder walls.
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Re: ma scoot has the sputters! NH80 problems

Post by b1jackson »

its the worn rings that causes the piston slap and the scuffs on the side of the piston isn't it?
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Re: ma scoot has the sputters! NH80 problems

Post by Bear 45/70 »

In most cases it is a worn cylinder (usually developed a taper in the bore) that causes piston slap. I have never heard of rings causing it.
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Re: ma scoot has the sputters! NH80 problems

Post by b1jackson »

Parts are all ordered. Hopefully here on Friday so I can get it back together on the weekend.
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Re: ma scoot has the sputters! NH80 problems

Post by b1jackson »

grrrrr :evil: rings are backordered..everything else is in!
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Re: ma scoot has the sputters! NH80 problems

Post by b1jackson »

OK. Rings came in and now have the scoot all back together. Tried to fire it up but it doesn't seem to be sucking (or drawing) fuel from the tank into the carb. I haven't cranked it over too too much but would there be a reason why fuel doesn't seem to be flowing? I don't want to crank excessively on a dry new piston. When I had the motor out, I didn't disconnect any of the vacuum hoses. I just hung the carb and bystarter off to the side when I had the head off.

Just had a thought. Is it possible that I turned the reeds the wrong way? Had them out just to look at them. I know they are not upside down but wonder if I have them turned and facing the wrong direction.
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