Hey Everyone! I hope you can help me out here...My bike has a NT Carb that was a solution to a problem with my original carb from the bike kit that I got on ebay. The bike was working really well, but I got a nail stuck in my tire...replaced the wheel about a week later. I go for a ride and about a half mile exactly at about 1/2 throttle-3/4 throttle, my engine starts getting quieter and slowing down. It was as if it was out of gas. I checked the gas in the fuel filter, but the filter is full - meaning there is no lack of fuel flow on that end. Now wait- it gets stranger! I figured out that when I get to that point where it slows me down, I can stay off the throttle and the bike accelerates by itself at about 5-15 mph depending whether I'm level or going uphill. Also, when it starts to accelerate itself and I disengage the clutch, the bike revs up. As I hit the kill switch, it knocks! I can't understand it! Could it be bad gas? I got it from a gas station that had closed down for a month and just reopened. I know the best are on this forum! Please share your thoughts!
Strange Problem - Engine slows down after mile
- Thread starter vinnie
- Start date
Bad gas, air leak, there are several problems that can cause this.
Check your intake for leaks and replace the fuel with some fresh and see what you find.
Personally, I'd be checking for air leaks anytime the engine revs by itself.
The knocking sounds like a lean condition which results from air leaks.
Check your intake for leaks and replace the fuel with some fresh and see what you find.
Personally, I'd be checking for air leaks anytime the engine revs by itself.
The knocking sounds like a lean condition which results from air leaks.
Okay. I will check the engine and its components for an air leak. I just thought I would mention that I also have to run the bike with the choke on full. If I open the choke, the bike will slow itself until it turns off. Does that also make you think it is an air leak? I imagine if it were an air leak, the air would be flowing better into the piston cylinder the more I open the choke. Thank you for your quick response, by the way!
Check your gas cap to make sure its venting properly . When your engine starts acting up like you said , crack open the gas cap for second or two and if its goes back to normal I don't think you know what it is .. Also check the head that it torque to spec.
if you have to run it with the choke closed, it's almost certainly an airleak. the air is getting in somewhere besides the carb throat.
Okay, here is my update:
I was wrong about the choke. I took apart the carb and realized that I thought it was closed when it's actually on open. I think my old carb may have been that way and I never noticed. Regardless, I made a discovery while taking the carb off the bike. The gasket between the piston cylinder and the intake pipe has a rip. I retightened it with the gasket as close to normal as possible just for the time being. How should I check for other places leaking air? I've read to use carb fluid, but I do not have any here with me right now.
I emptied the tank and got fresh gas from a different gas station and mixed the oil in. The bike idled fine after I started it and got off to see how it was. About a mile and a half later, it started revving very high again. If it is just that one location...it might be since the engine got warmed up, the metal expanded and opened a gap where the gasket is ripped
I was wrong about the choke. I took apart the carb and realized that I thought it was closed when it's actually on open. I think my old carb may have been that way and I never noticed. Regardless, I made a discovery while taking the carb off the bike. The gasket between the piston cylinder and the intake pipe has a rip. I retightened it with the gasket as close to normal as possible just for the time being. How should I check for other places leaking air? I've read to use carb fluid, but I do not have any here with me right now.
I emptied the tank and got fresh gas from a different gas station and mixed the oil in. The bike idled fine after I started it and got off to see how it was. About a mile and a half later, it started revving very high again. If it is just that one location...it might be since the engine got warmed up, the metal expanded and opened a gap where the gasket is ripped
yeah replace that intake gasket and drill a 1/16th inch hole in the center of your gas cap. that eliminates two potential probs. I reccomend with an NT carb you use a rubber "O" ring
http://thatsdax.com/ENGINE_KIT_PARTS_PAGE_2.html or at your local hardware store. (bring carb with you and try a couple for fit.
Pull the carb and the manifold together off the engine... loosen the screw/nut holding them together - then place manifold and carb plus O ring but minus air filter in a bench vise and very slowly and carefully squeeze both together snugly. You will see them squeeze together in the vise. Do this carefully. When fully snugged, tighten the screw and bolt, while in the vise, then reinstall as one back on bike. These 3 things will assure no vapor lock and air leaks. Go from there.
http://thatsdax.com/ENGINE_KIT_PARTS_PAGE_2.html or at your local hardware store. (bring carb with you and try a couple for fit.
Pull the carb and the manifold together off the engine... loosen the screw/nut holding them together - then place manifold and carb plus O ring but minus air filter in a bench vise and very slowly and carefully squeeze both together snugly. You will see them squeeze together in the vise. Do this carefully. When fully snugged, tighten the screw and bolt, while in the vise, then reinstall as one back on bike. These 3 things will assure no vapor lock and air leaks. Go from there.
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I agree. replace the ripped gasket.
You can easily make your own gasket from thick aluminum roaster pan from any dollar store.
You can easily make your own gasket from thick aluminum roaster pan from any dollar store.
for the intake gasket, you can buy a roll of grey gasket material at any auto parts store for a coupla bucks. you'll have enough to make a thousand gaskets. buy some carb cleaner while you're there.
the o ring trick works, but i wouldn't squeeze it in a vice like mentioned above. the carb tabs break really easy. you can push it together by hand easy enough.
i'd also pull the head off and check your head gasket. you'll see black burn marks across the gasket if it's leaking.
the o ring trick works, but i wouldn't squeeze it in a vice like mentioned above. the carb tabs break really easy. you can push it together by hand easy enough.
i'd also pull the head off and check your head gasket. you'll see black burn marks across the gasket if it's leaking.
Alright, here is my update:
I went to the hardware store and picked up a few things. First, I got O-rings for the carb and intake pipe. I could not get the O-ring to fit in-between the outside of the carb and the inside the intake pipe. So, that picture on the link that was provided above is exactly how my carb is. I pushed it by hand as far as I could with pressure and tightened it shut. I figure that will still be effective since it forms a lip around the edge of the intake pipe - blocking air from getting around it
I also picked up some gasket paper, but I'm not sure if I can actually call it gasket paper. I asked the guy at the hardware store and he showed me this 1 cm thick gasket and I said I need much thinner material. He knows me from my bike, so he brought me to the back where he had this really thick paper- like card-stock. He told me he uses it on his moped all the time as gasket paper. He gave it to me for nothing, so I cut out the gasket cutout and compared it to the old gasket. They are about equal in thickness. What do you think of using it as a gasket?
I did not get to check the head gasket yet...ran out of daylight!
I went to the hardware store and picked up a few things. First, I got O-rings for the carb and intake pipe. I could not get the O-ring to fit in-between the outside of the carb and the inside the intake pipe. So, that picture on the link that was provided above is exactly how my carb is. I pushed it by hand as far as I could with pressure and tightened it shut. I figure that will still be effective since it forms a lip around the edge of the intake pipe - blocking air from getting around it
I also picked up some gasket paper, but I'm not sure if I can actually call it gasket paper. I asked the guy at the hardware store and he showed me this 1 cm thick gasket and I said I need much thinner material. He knows me from my bike, so he brought me to the back where he had this really thick paper- like card-stock. He told me he uses it on his moped all the time as gasket paper. He gave it to me for nothing, so I cut out the gasket cutout and compared it to the old gasket. They are about equal in thickness. What do you think of using it as a gasket?
I did not get to check the head gasket yet...ran out of daylight!
Yes use the moped guys advice. Make your Gasket re-assemble, give her a go and tell us the results.
I feel your pain....crap. is that me? jeez... ya build one moped and you're labeled for life...
I drive to court naked and drunk with seventeen chickens in the car ONE time and everybody calls me Maniac.
It's not fair.
Alright Everyone...Here is my update: I cut out the new gasket for the intake pipe and also installed the o-ring in the intake to carb connection. The bike has been running very well. When I was having the issues before the change of parts, I would go about 15-20 mph for a half mile and the issues would start. Now, I went a mile at about 25mph and didn't have a problem any of the 4 times I did it. Here is my latest issue, though:
My clutch lever pops up from, what I believe to be, the vibrations from the bike. I carry a screwdriver with me to open the clutch cable area cover and reinsert the lever into place. When it pops up, I can't disengage the clutch and I have to pull onto grass and stall out the engine while going as slow as possible to prevent dragging my locked tire on the pavement. Any advice for stopping this issue? Thanks a lot
My clutch lever pops up from, what I believe to be, the vibrations from the bike. I carry a screwdriver with me to open the clutch cable area cover and reinsert the lever into place. When it pops up, I can't disengage the clutch and I have to pull onto grass and stall out the engine while going as slow as possible to prevent dragging my locked tire on the pavement. Any advice for stopping this issue? Thanks a lot
The clutch actuator arm (cam) is held in the cover by a pin. These pins can and do come out which allows the cam to lift out of the side cover.
The pin is approximately 3/32" in diameter and some were held in by a glob of epoxy and some were peened in. You can make a new pin using the shank of a 3/32" drill bit or similar piece of steel. Some have tried a roll pin and others something as simple as a nail.
Whatever you use it must be secured to keep it from falling out. I prefer to cut the pin short and peen the top edge of the hole so the pin can not come out. I don't trust glue.
The cam can be inserted or removed by turning it so the flat area clears the pin then rotated back to the position it needs to be to actuate the clutch. Caution: don't loose the steel pin that protrudes from the center of the drive sprocket or the ball bearing that rides behind that pin. Both also need to be well lubricated.
Good luck.
Tom
The pin is approximately 3/32" in diameter and some were held in by a glob of epoxy and some were peened in. You can make a new pin using the shank of a 3/32" drill bit or similar piece of steel. Some have tried a roll pin and others something as simple as a nail.
Whatever you use it must be secured to keep it from falling out. I prefer to cut the pin short and peen the top edge of the hole so the pin can not come out. I don't trust glue.
The cam can be inserted or removed by turning it so the flat area clears the pin then rotated back to the position it needs to be to actuate the clutch. Caution: don't loose the steel pin that protrudes from the center of the drive sprocket or the ball bearing that rides behind that pin. Both also need to be well lubricated.
Good luck.
Tom
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I tried making a pin- it has not worked out for more than a 2 miles of riding. I am going to try the drilled hole next, since my pins keep falling out. As long as it fits with the gear on the inside, I think it will work.
On another note, I checked the head gasket for black marks. It does not show any signs of a vacuum leak. The weather has been about 20 degrees cooler than it had been when I was having the problems with the vacuum leak when I started this post. I rode my bike yesterday at about 25-30 mph 3 miles and just as I was arriving at my destination, the engine slowed itself down. When I pulled the throttle for more gas, the bike slowed down even more. When I let go of the throttle, it went back to normal RPMs. I checked the gasket by the clutch cover and that is in tact and seems to be fine. What do you think it could be? It seems to happen the most when the engine gets very warm. Thanks
On another note, I checked the head gasket for black marks. It does not show any signs of a vacuum leak. The weather has been about 20 degrees cooler than it had been when I was having the problems with the vacuum leak when I started this post. I rode my bike yesterday at about 25-30 mph 3 miles and just as I was arriving at my destination, the engine slowed itself down. When I pulled the throttle for more gas, the bike slowed down even more. When I let go of the throttle, it went back to normal RPMs. I checked the gasket by the clutch cover and that is in tact and seems to be fine. What do you think it could be? It seems to happen the most when the engine gets very warm. Thanks
Don't know, I've had that deceleration issue as well, then it went away, perhaps I need a new fuel filter? My thoughts are that some dirt clogged my filter and then dislodged, or my fuel lever was not on all the way.
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And if you are in the field and blow an intake or an exhaust gasket, you can make one out of a stiff piece of cardboard, i had a beer box in my back pack as a liner (and for more beer).
Well, the beer box gasket on my intake got me home.
I wasn't gonna walk!
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And if you are in the field and blow an intake or an exhaust gasket, you can make one out of a stiff piece of cardboard, i had a beer box in my back pack as a liner (and for more beer).
Well, the beer box gasket on my intake got me home.
I wasn't gonna walk!
With my deceleration issue, it definitely has something to do with the engine temperature. On a hot day, it happens much faster than on a cold day. When it starts to decelerate, I can only very slightly pull the throttle to keep moving at a slow speed. I still can't figure out what it is