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Makotosun

Fuel in Exhaust?

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Replied by mdscott on topic Fuel in Exhaust?

Not sure it would help, but maybe video the starting of the bike, worth a shot.
Thanks Mark
Roseville, Ca.

'03 ST1300
'75 Norton
'73 CB500K
'81 Honda CT110
'87 PW50
'64 McClane Edger
'02 Honda XR70R
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21 May 2020 17:22 #31

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Replied by MarkT on topic Fuel in Exhaust?

Yes, video would help.

I seriously doubt a new ignition is the solution. That magneto is a very reliable system.

Couple things here... It takes a lot of fuel to have it puddle in the pipe. There is no way the pipe is filling up with fuel repeatedly unless the crankcase is still full of fuel or you're mistaken and there is something wrong with the petcock and/or float needle/seat/float level.

And if the crankcase is still full of fuel, it could only have got that way if the petcock was bad or left on and/or the float needle/level is causing flooding.

The "revving up high" is counter to what a badly flooded engine will do... that sounds like an air leak. A case full of fuel will often damage or push out a crank seal by hydraulic pressure... and if you have fuel in the pipe you definitely have a case full of fuel.

All I can say is go back to basics. Make sure all the fuel is out of the crankcase. Pressure test for air leaks. Check the timing. Float level and jetting at stock specs. Unrestricted air filter (rag not forgotten in air box, clean and oiled properly if foam, element not old/deteriorated if paper or foam) Known good spark plug.

And if after you're sure the crankcase is empty of fuel and the pipe keeps filling up after you try to start it? You definitely have a float needle/seat and/or petcock issue.
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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21 May 2020 22:00 #32

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Replied by Cruiser84 on topic Fuel in Exhaust?

I removed the top end yesterday to get a better idea of what was going on underneath. Not much carbon build up and the cylinder wall looked good and felt smooth. The last photos show the crank case and the inside of the cover that looks like it was patched at some point by the PO... not sure if this could be the culprit?

As for the fuel in the tail pipe, I have removed it several times after long kicking sessions to confirm that I was not getting excess fuel in the pipe. I am however sometimes getting backfires through the exhaust and/or the carburetor, which leads me to a jetting or mixture problem(?). I am running stock size jets and am 1 ½ turns out on the air/fuel screw.

I'll post a detailed video Monday that will hopefully uncover the mystery. In the meantime, hope you all have a great Memorial Day weekend, thank you to all our vets on here and ride on!
22 May 2020 10:53 #33

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Replied by mdscott on topic Fuel in Exhaust?

It looks like there is a crack in the case. I can't tell but does the crack go into the transmission area?
Thanks Mark
Roseville, Ca.

'03 ST1300
'75 Norton
'73 CB500K
'81 Honda CT110
'87 PW50
'64 McClane Edger
'02 Honda XR70R
Last edit: 22 May 2020 11:07 by mdscott.
22 May 2020 11:06 #34

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Replied by Cruiser84 on topic Fuel in Exhaust?

There's not a crack, just a blemish or discoloration, but there was definitely a patch job... as if a hole was bore through it.
22 May 2020 11:09 #35

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Replied by Cruiser84 on topic Fuel in Exhaust?

First off, thank you all for chiming in and helping this newb learn a thing or two... or one hundred. Video is still coming.

Just got a NOS float arm to go with the NOS needle valve. Fuel is back to flowing the way it should and it appears there is no longer fuel getting into the exhaust.

Crankcase shows no evidence of fuel and petcock is not leaking or seeping.

Now for the life of me I can’t get her to kick over. Spark, compression, fuel and carb are all in what appears to be good and normal working order.

A mechanic in Portland attests that a 50 year old mag can not be reliable. The experienced folks on here beg to differ. I’m not exactly ready to drop $95/hr to let the guy change a bunch of functional OE parts, but i’m at a loss where to start or go back to.

Any one in the Newberg/Portland area? Case of beer and an ear bending grin for who can get her going.
30 May 2020 13:25 #36

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Replied by Swoop56 on topic Fuel in Exhaust?

I haven't re read all the posts , so this may have been mentioned before .
Now that your fuel level in the float bowl is correct , the starter jet in the bottom of the float bowl
needs to be clear, to richen mixture for starting .
They are very small , so block easily . especially if left sitting in fuel for extended periods .
As I said , you may have already been through this earlier , but if not , it might be your problem now .
30 May 2020 14:55 #37

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Replied by RT325 on topic Fuel in Exhaust?

somewhere there i think you said backfiring in the exhaust which straight away leads me to think its broken a flywheel crank key, providing points are opening. sorry i've probably been here and said that before.--carry on lol.
30 May 2020 18:20 #38

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Replied by Cruiser84 on topic Fuel in Exhaust?

I'll have to inspect the flywheel crank key, but I believe it is sound....fingers crossed.

@swoop56, I will pull the main jet and give it a double check and possibly swap it out with another of the same size to see if that makes a difference.
31 May 2020 12:06 #39

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Replied by Swoop56 on topic Fuel in Exhaust?

The jet I was referring to wasn't the main jet , it was the starter jet .
It has a pickup in the bottom of the float bowl , and sits inside a tunnel
going up to the gasket surface .
I can't do pics , but maybe someone else will chime in with one .
A pic is worth a thousand words .
A main jet has no effect on starting circuit .
31 May 2020 14:10 #40

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