Hi everyone, I'm new here and to motorised bikes and have a slight problem.
Basicly I think I have an air leak (a small one) but first a quick intro and history around the problem. (I did search the forum before posting btw
)
Me and my friend built up the bike fine but when the engine was mounted and the carb in place the air filter box wouldn't fit as the seat tube was blocking it. At first I just ran it with the plastic spacer and sponge but eventually decided that in wet conditions the air filter box was needed. I wanted to re mount the engine to try and accomdate it but my friend suggested another idea which we followed out. What we did is trimmed the intake manifold by a few mm and cut down the airbox. The air box is now able to be mounted to the carb and one screw was cut down to allow the choke to be moved up/down. Since the airbox was cut there is a gap between it and the outer area of the carb so I taped it up with duct tape to stop any water getting onto the sponge and into the carb.
With all that done I rode home happily but then came the irratic idle and high revs and by the time I got home (not a very long ride) a hotter than normal engine. We knew it must be an air leak so the next day we put two 'O' rings between where the carb and manifold join. Before I can continue the method I used to check if there was a leak was to run the engine until warm and lift the choke to full, if it cuts out all is good but if it still runs then theres a leak right? How reliable is this method btw? Anyway it didn't cut out but it wanted to, and the rpm was quite low.
Finally today I went to buy some Instant gasket paste to use to eliminate the air leak between the carb and manifold. I don't know what the equivalent in the US is but it's a blue gasket silicone like paste (link). We placed it on the end of the manfifold and all around and let it set, then attached the carb back on. We then started the engine and ran it till it was warm, and hoping our efforts payed off that when we lifted the choke up the engine would cut out, but no luck....it was nearly there however. This is where I am now. The rpm is very low and the engine will cut out with a very slight twist of the throttle (after it is warm and the choke is fully up) Another thing I forgot to mention is we replaced the intake gasket as the old one was ripped and used gasket paper for it![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Well I have ran out of ideas and hope that someone may be able to help me. Any other ways of checking or knowing if it's an air leak? Does the engine always cut off when the choke is lifted after a warm up? My friends engine cuts off instantly. Any other areas I should check or maybe use more gasket paste around the carb and manfiold? I really want to get this sorted so any help will be appreciated.
Very long post but more detail is better right....?![Big Grin :D :D](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Thanks in advance![:ride2: :ride2: :ride2:](https://motorbicycling.com/images/smilies/ride2.gif)
Basicly I think I have an air leak (a small one) but first a quick intro and history around the problem. (I did search the forum before posting btw
Me and my friend built up the bike fine but when the engine was mounted and the carb in place the air filter box wouldn't fit as the seat tube was blocking it. At first I just ran it with the plastic spacer and sponge but eventually decided that in wet conditions the air filter box was needed. I wanted to re mount the engine to try and accomdate it but my friend suggested another idea which we followed out. What we did is trimmed the intake manifold by a few mm and cut down the airbox. The air box is now able to be mounted to the carb and one screw was cut down to allow the choke to be moved up/down. Since the airbox was cut there is a gap between it and the outer area of the carb so I taped it up with duct tape to stop any water getting onto the sponge and into the carb.
With all that done I rode home happily but then came the irratic idle and high revs and by the time I got home (not a very long ride) a hotter than normal engine. We knew it must be an air leak so the next day we put two 'O' rings between where the carb and manifold join. Before I can continue the method I used to check if there was a leak was to run the engine until warm and lift the choke to full, if it cuts out all is good but if it still runs then theres a leak right? How reliable is this method btw? Anyway it didn't cut out but it wanted to, and the rpm was quite low.
Finally today I went to buy some Instant gasket paste to use to eliminate the air leak between the carb and manifold. I don't know what the equivalent in the US is but it's a blue gasket silicone like paste (link). We placed it on the end of the manfifold and all around and let it set, then attached the carb back on. We then started the engine and ran it till it was warm, and hoping our efforts payed off that when we lifted the choke up the engine would cut out, but no luck....it was nearly there however. This is where I am now. The rpm is very low and the engine will cut out with a very slight twist of the throttle (after it is warm and the choke is fully up) Another thing I forgot to mention is we replaced the intake gasket as the old one was ripped and used gasket paper for it
Well I have ran out of ideas and hope that someone may be able to help me. Any other ways of checking or knowing if it's an air leak? Does the engine always cut off when the choke is lifted after a warm up? My friends engine cuts off instantly. Any other areas I should check or maybe use more gasket paste around the carb and manfiold? I really want to get this sorted so any help will be appreciated.
Very long post but more detail is better right....?
Thanks in advance
![:ride2: :ride2: :ride2:](https://motorbicycling.com/images/smilies/ride2.gif)