Loss of high RPM spark?

Pablo, what brand of engine is this? I've had a couple bum engines in my 30+ builds I've done over the past couple years. My most recent bad engine was very similar to what problems you are having. Lucky for me, this vendor had a 30 day warranty and I got a new one...problem fixed. I tried everything with that engine to no avail.
 
Skyliner70cc said:
Pablo, what brand of engine is this? I've had a couple bum engines in my 30+ builds I've done over the past couple years. My most recent bad engine was very similar to what problems you are having. Lucky for me, this vendor had a 30 day warranty and I got a new one...problem fixed. I tried everything with that engine to no avail.
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I have no idea as to brand. Just Chinese knock off. This is the guy I bought from (recommended by Ghost0) and exactly what I bought. Supposedly "improved" kit: 80cc Motorized Bicycle Bike Motor Moped Kit Engine NR - eBay (item 150228317748 end time Mar-24-08 14:17:57 PDT)
 
I just now sent the seller an email. Not sure what good it will do....but good gawd, I shouldn't need a whole new engine!
 
So before Church I just pulled the rotor off. First the bearing seal looks fine. There was a little half moon key, everything looked OK, but the slot in the rotor sure is generous - ie the rotor isn't solidly keyed....you can wiggle it pretty good on the shaft without the nut. Is this normal?

Also there was lots of iron FOD stuck to the magnetized shaft, rotor, nut...looked like shavings and removed threads. That can't be good, but I doubt it has anything to do with "the problem".

Used the rope trick to get the nut off.
 
I think the new kit things means they improved the engine design slightly and all the newer versions have some bearing so all the dealers are now selling the improved kits as if it was something they did themselves.
 
deacon said:
I think the new kit things means they improved the engine design slightly and all the newer versions have some bearing so all the dealers are now selling the improved kits as if it was something they did themselves.
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It's marketing. I put the magneto works back in.

Just curious - what would a backwards rotor do? What symptoms? Seems like the timing would be so off it wouldn't run??
 
I haven't tried it either but some day I'll get curious it may not run very well or no change then again it might not run. I'll try it soon you got me to wondering. It might make it have super powers or something rotfl My first guess is I'll just wear out the screws, nut/bolts all in the name of science.
Norman
 
Pablo said:
Also there was lots of iron FOD stuck to the magnetized shaft, rotor, nut...looked like shavings and removed threads. That can't be good, but I doubt it has anything to do with "the problem".

Used the rope trick to get the nut off.
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Pablo- In my diatribe about what to do to these kits before you run them mentions cleaning the mag with brake or carb cleaner....that's because on both new kits I got, when I pulled the cover and sprayed then, they were full of crud. Not good for the mag.
 
Bikeguy Joe said:
Pablo- In my diatribe about what to do to these kits before you run them mentions cleaning the mag with brake or carb cleaner....that's because on both new kits I got, when I pulled the cover and sprayed then, they were full of crud. Not good for the mag.
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Yes - great point. There was some pig fat on the magneto arms as well....
 
Pablo said:
I have no idea as to brand. Just Chinese knock off. This is the guy I bought from (recommended by Ghost0) and exactly what I bought. Supposedly "improved" kit: 80cc Motorized Bicycle Bike Motor Moped Kit Engine NR - eBay (item 150228317748 end time Mar-24-08 14:17:57 PDT)
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I've actually met this seller. He had a booth at the 2007 Grand Rapids Autorama, I talked to him for several minutes and checked out the bikes that he had on display. The bikes looked nice and he seems like a good guy, the one thing I noticed about his display was that some of the pictures he was using to promote his business were othre peoples bikes that I knew. I'm noe 100% positive but I think one of the bikes on his e-bay ad was built by Kevin Waddle, the same guy that did my polished engine. Mike Simpson could probably verify this...Kelly

Bike in question
80ccbike.jpg
 
I just checked the photo gallery on the frapper map I set up and here is Kevins (mypetelvis is his screen name) bike Frappr Maps - My Maps . I don't want to speak ill of the seller but feel that if they are selling a product and want to show kustom work to promote sales, they should show their own work or at least credit the builder/owner:-||...Kelly
 
Vely intellesting.

Anyhow - I fired it up. Ran a bit better - and the strange scraping noise was gone. All I did was de-burr and clean up the rotor, and one thing I didn't mention was it looked like the rotor had contacted the side on the motor from time to time. Probably took care of that.

Started right up as usual but it was still doing it's cranky chokeness and funny throttle tricks. The float still needs that very tiny tweak, but I didn't feel like getting all fuel smelly like, as I had my Easter suit on and guests were waiting with homemade cheesecake inside.

With the longer photoperiod, when I get home tomorrow I'll tear the carb apart again..........:-{:eek:
 
Someone who has better engine knowledge will have to answer this but... would a cracked head cause a bike to run lousy top end. I have had cars with head gaskets blown that run like crap but they have water and exhaust issues as well.
 
I've never done it myself but I would imagine that yes it would run like crap. I would guess that you would lose compresion and lose power all the way around...Kelly
 
I'm thinking a thin coat of gasket maker on each side and re-torque or order/make a new one and test it.

NORMAN!

I think Norman made some before.
 
If it isnt glued down I would just remove it put some sealer to fill in the poor workmanship at the machine shop and retorque it. It's actually pretty minor compared to all you have done so far.

When I tore my head and pot off, I sealed it with bearing grease. Not sure why but it worked just fine. I would use a high temp sealer now though.
 
Let me finish dinking with the carb.....I'm going home in less than 1 hour.....change, hug the wife....get fuel soaked!!:p
 
I try not to use gasket sealant if the gasket is a good quality one it will seal. Pablo did you also check the intake manifolds surface for being flat? You can do it the same as the intake on the cylinder. If you have a head leaking it will show up as nasty black oily stuff oozing out where the head and cylinder mate. Best way to fix that is with a new head gasket and use an inch pound torque wrench. You sell a high quality oil so I expect you to borrow or buy a good torque wrench if you need to pull the head. The head shouldn't have a crack but the top of the cylinder is not machined and pretty rough I wet sand the cylinder on glass using 220 grit wet/dry to smooth it out and I use water with a dash of liquid soap to lube and keep the sanding paper clean. I also coat the head gasket with a cheap aluminum spray paint which works like a gasket sealer let it dry or put it on wet its up to you. torque for the head which I use is 40 then 80 then 110 inlb. in an x pattern. warn it up good and after its stone cold retorque it to 110 to 120 inch lbs. Make sure all the cylinder studs are all screwed in the proper amount use the double nut method to seat the studs firm but not screaming tight.
 
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