can't find an answer then ask here someone may be able to help!!

[Norman]

I would try to bend the pipe and if you can afford it see if you can get a tuned pipe they do more for these bike engines than most of the performance mods. A lawn mower muffler might work ok I haven't tried one I made myself a sort of tuned pipe for all my bikes with an attached muffler to keep the neighbors happy and so I don't go any more deaf.
Norman

 

[CHIPS X]

Norman,

Do you know what size screw the carb idle screw is? Mine was backed out pretty far on the ride home and...gone. Now I'm running but she dies with every clutch engagement. Can you or anyone help? I have a Fastenal down the street so I bet I can fix it today if I can figure the size out! Thanks for all the help everyone! Chips

 

[Norman]

metric threads 4m dia. 0.7 threads

hope this will help
Norman

 

[furament]

hay norm u ever have a problem whith the thing overheating? my old 49 will run around the block get warm and die out just started doing this and im at a loss it usialy runs nice could it be a lack of oil? or is there such a thing as bad 2 stroke oil?

 

[Norman]

plugged fuel filter or the in tank fuel strainer? cdi about to go south? old fuel sitting for
a long time in the tank? almost fowled spark plug?

 

[barron909]

I have a 80/66 cc motor and the throttle twists but I don't even need to touch the throttle and the motor runs on it own, basically can just cross my arms and let the motor take me away as I balance myself. I wanna change that so when I don't touch the throttle, the engine doesn't drive just runs due to me pedaling and when I twist the throttle I can stop pedaling and let the motor take over...How do I tighten the cable or whatever it is I need to do...If this all made sense?

 

[furament]

soo i went through the 48 cleened out the lines tank and carb new gas it runs but the choke is different now with 2 rings and new jug that might change wen i get the new setup broke in it coughfs out the carb???? and bougs down when warm i dunno would u worry abought a distinct knok rattle from a new 80 if the bottow end seems good its not broke in ether but it started to make bad sounds??

 

[Norman]

did you change out the cylinder and reuse the old piston? if you did what is the measurements of the old piston vs the measurements of the new cylinder. If you have too much clearances the piston will rattle. I referring to thousands of an inch which isn't much the piston is supposed to run will very little clearances. you need to measure the piston 90 degrees to the wrist pin top middle and bottom. measure the cylinder top middle and bottom.

 

[barron909]

How do I fix my throttle problem? It looks like it's too lose and the flow is not being blocked or something because without touching the throttle grip it runs on it own...Is that normal? This is my first motor.

 

[NickDK]

Hey Norman,

Please see my current thread: http://motorbicycling.com/f3/help-my-custom-exhaust-11335.html

I haven't received much insight and I would very much appreciate your expertise! Thanks a BILLION!



- Nick

 

[Norman]

Nick
If your exhaust makes you happy and doesn't make other people mad for being too noisy then that is cool. Its fun to change things isn't it.
Norman

 

[NickDK]

You bet! Tinkering with my MBs is my number one hobby. Thanks for the 10-4, Norm, that's just what I was looking for.

 

[NickDK]

Norman,

Here is one for you. I have an older bike...one of my first builds. Its a 67/80 cc 2-stroke. It probably has about 1000 miles on it. It has been running great for the past two years until all of sudden this week it lost all of its power and it won't even stay running without holding the throttle wide open. Even at WOT it barely idles! I did the standard routine and checked the plug, wires, carb, filters, fuel, etc and even looked at the cylinder walls to make sure I didn't really mess something up. Everything was fine. I removed the cap from the muffler to clean it out and I decided I would take it for a spin (without the cap on the muffler). BAM, all of the power is back and it idles like normal. I cleaned out the muffler very well assuming it was just clogged and repaced the cap. I went out for another spin and I was back to square one...the bike will not idle unless holding full throttle and won't push past 5 mph. I know what you are thinking...the muffler is clogged and the clog is bypassed when I remove the muffler cap. Thats what I thought. So I replaced the muffler with a brand new stock muffler. I took it out for a spin and same thing happened...I got no power. I removed the cap from the brand new muffler and went out again...just as expected all my power returned. What is going on here?

- Nick

 

[Norman]

did you check the main seals on the crank? if when you take off the case covers and find a black oily poo then you will know if its leaking bad.Hard to say why the exhaust makes it not run I haven't found one to have the exhaust plugged. What does the exhaust port look like any carbon build up at the exhaust port?

 

[NickDK]

I've never taken the bottom end apart on one of these...which doesn't mean I wont do it!

As far as the carbon, yeah there is a lot of buildup on top of the cylinder, at the exhaust port, and around the muffler mount of the muffler. I took the cylinder head off again to take a closer look and I discoverd a couple gouges on one side of the cylinder wall that are big enough to feel just by rubbing your finger across -- but just barely feel them. Do you think maybe something got in there and caused a couple gouges and now I have less compression? If so, how does reducing exhaust back pressure make it run better?

Thanks again Norman, you are such an asset to this forum!

 

[Norman]

well thats one I'm not sure of( lowering back pressure to get back lost power?) Something changed on the engine I wonder if just cleaning the carbon build up out of the exhaust port will help?
Best way for compression checks is with a compression gauge, by feel your just guessing. gouges or grooves in the cylinder walls will allow gases to get by the rings so there will be a loss of power there. Hard to say just what got in there and caused the scoring Did you check to see if the ring locater pins are still in the piston? I've seen one piston where the pins were inset too deep and the ring could go over the pin.

bad thing about these engines if you tear up the cylinder then you will need a new cylinder. As these are chromed but the good thing is replacement cylinders are cheap but a whole replacement engine is not much more. So you will have to decide what repair route is best for you cost wise.

 

[NickDK]

Ah, well I have a spare engine laying around with only about 100-200 miles on it. I will swap em out and tear down the old one. If I find anything interesting I'll take some pics and post em here for ya though I may not get around to it for a couple weeks.

Oh, and just cuz Luke is my Avatar does not make you my sworn enemy (nor my father)! I'm a lego dealer which is the reason for the Lego Luke avatar. Cheers!

 

[Norman]

The reason for the the Darth Vader avatar is a long story.
Norman

 

[pedal pusher]

Norm,
At this point I would rather err on the side of caution, so I am proceeding very cautiously at this point with my first build Huffy, same as Cranbrook.

I am ready to mount clutch lever and cable. I know the big spring is a heat shield for the clutch cable. Also in the bag is a rather sturdy spring like a firearm spring about 4mm by 81 mm long. The Gasbike instructions don't mention this spring. What is is for? Also in the bag is a strange fitting looks like a threaded reducer with a 10mm bolt in the in the larger end, the larger end about 27 mm and the smaller end about 19mm with about 23mm place for wrench in middle. What is this? Important?

It still looks to me like the clutch cable will be exposed to high heat inspite of the spring.

Thanks much.
D. J. Price
answer to your questions
the small long spring is a sort of return spring or anti rattle spring it goes on the clutch cable between the clutch arm and the clutch cable lower mount right over the cable.
I think the other item you are asking about is the puller for the sprocket and gear puller.
I have not had a problem with the clutch cable getting toasted by the cylinder where it touches.
I do try to grind the spot at the edge of the cylinder so the cable isn't bent as it goes by the cylinder. Some builders don't use the small spring either on the clutch return But I do.
Norman

 

[80ccBlueRay]

hey wuts up, i bout a 80cc kit from bikeberry. install went well, a few alterations but went together. it was yesterday when i got it runnin.. today i was ridin it for about 10mins, sounded like it backfierd, or i thought i heard sum wierd sparkin noises, but not sure. went to hit the kill switch so i can coast to hear it idle, but it cut off. now it wont start...i went home, found you guys, and looked up everything i thought could be wrong with it, but no luck... when i hit the kill switch and give it some gas, it seems to want to start but pops, and misfires, sum black smoke, but wont stay runnin..
i resoderd the connections, checkd the carb ect, i noticed the wires comin from the magneto, looked kinda arched. thinkin this might be an electrical problem..

any suggestions?

the pop you heard might be your head gasket starting to leak you will need to check the head see if the nuts are loose. to fix the the head check out some of my posts the total tear down might help for the head gasket. you can also check to see if by chance the the kill switch is not shorting out by disconnecting it and see if then the bike will run. also the choke. when the lever is up the choke is on. When the choke lever is down the choke is off for normal riding.
Did you mix your gas in a can? or in the tank? Best to mix the gas in a can and at a 20 to 1 mix I like to use a 32 to 1 myself. I like the 40 to 1 mix syn. oil after breaking it in I've been using the polan syn oil lately(sold at Walmart) at the 40 to 1 mix(even with a bushed wrist pin engine) and find that it gives me a pretty good running engine and no smoke. I also run plain old regular gas no need for the high octane stuff. Good luck.
Norman