high speed performance weirdness
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Cruiser
Joined: Jan 2007
Posts: 209
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From: Fort Campbell, KY
high speed performance weirdness
Sometimes, but not all the time and it seems to be when the engine is good and warm from riding, after I've been doing 55 -65 for a minute or so, I lose power and I can hear a popping comming from the exhause pipes. At the same time, the valves (or maybe it's not the valves) seem to knock loud in the engine, but not real, real loud(something in the engine knocks anyway).
When it happens I let off the gas, andit stops in asecond or two and everything returns to operations normal.
This winter I did a lot of work. Rebuilt carb, replaced all oil hose lines, but I didn't have to do any engine maintenance.
It seems weird. Maybe the high speed jets on the carb are out of adjustment? The knocking from the engine concerns me. My oil level is good.
I figureit could be 3 things. Not getting enough oil at high speeds, not enough fuel at high speeds, or not enough air at high speeds.
Any suggestions would be appreciated a lot.
Thanks.
When it happens I let off the gas, andit stops in asecond or two and everything returns to operations normal.
This winter I did a lot of work. Rebuilt carb, replaced all oil hose lines, but I didn't have to do any engine maintenance.
It seems weird. Maybe the high speed jets on the carb are out of adjustment? The knocking from the engine concerns me. My oil level is good.
I figureit could be 3 things. Not getting enough oil at high speeds, not enough fuel at high speeds, or not enough air at high speeds.
Any suggestions would be appreciated a lot.
Thanks.
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
RE: high speed performance weirdness
If something knocks in your engine, then you may have a serious problem. A knock is the term used to describe:
A bad connecting rod bearing(s)
Piston slap from worn bore(s)
Detonation from hot temperature and poor quality fuel with a low octane rating
On the otherhand, perhaps you may want to use another term to describe the condition.
Excessive valve clearance I would describe as a rattle or clacking noise. Valves do not knock. Pistons can knock. Rod bearings can knock. Once a knock starts it does not go away, nor is it likely to be intermittent. A knock only gets worse until parts fail and the engine is dead.
It is difficult for me to make an estimation of what the problem might be from the description so far.
Popping in the exhaust is usually because of an air leak in the inlet manifold O rings. This will cause the engine to lose power as well.
If it were me I would check the ignition timing and points gap to eliminate that. Make sure the inlet manifold is not leaking by squirting water on it while the engine is running at 1500 rpm or less. The engine will momentarily speed up if the water hits an area that has an air leak, because the temperary seal provided by the water puts the air/fuel mixture back in balance for a few seconds.
Myself, I do not think this has anything to do with the carb or the main jet setting, nor the float setting. If the float level was too high, gas will leak out. If it were too low, the machine might be affected in turns, but as long as there is enough fuel sitting in your float bowl bottom to feed the main jet, the engine is not going to notice it........pg
A bad connecting rod bearing(s)
Piston slap from worn bore(s)
Detonation from hot temperature and poor quality fuel with a low octane rating
On the otherhand, perhaps you may want to use another term to describe the condition.
Excessive valve clearance I would describe as a rattle or clacking noise. Valves do not knock. Pistons can knock. Rod bearings can knock. Once a knock starts it does not go away, nor is it likely to be intermittent. A knock only gets worse until parts fail and the engine is dead.
It is difficult for me to make an estimation of what the problem might be from the description so far.
Popping in the exhaust is usually because of an air leak in the inlet manifold O rings. This will cause the engine to lose power as well.
If it were me I would check the ignition timing and points gap to eliminate that. Make sure the inlet manifold is not leaking by squirting water on it while the engine is running at 1500 rpm or less. The engine will momentarily speed up if the water hits an area that has an air leak, because the temperary seal provided by the water puts the air/fuel mixture back in balance for a few seconds.
Myself, I do not think this has anything to do with the carb or the main jet setting, nor the float setting. If the float level was too high, gas will leak out. If it were too low, the machine might be affected in turns, but as long as there is enough fuel sitting in your float bowl bottom to feed the main jet, the engine is not going to notice it........pg
Thread Starter
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Cruiser
Joined: Jan 2007
Posts: 209
Likes: 0
From: Fort Campbell, KY
RE: high speed performance weirdness
Thanks for the replies guys.
There is the possibility that there is an air leak in the inlet manifold O rings since I had the carb off with the inlet manifold over the winter. That's one thing that I'll check.
Also, you mentioned the float. It runs really great except for the times when I have weird high speed performance. But you mentioned that if the float was out of adjustment (too high), then fuel would leak. If the float was adjusted too low then I would lose power in turns. I don't lose any power in the turns. But here is something that may be a factor. Fuel will leak from the overflow hose (I'm talking about the littlehose that comes from the float and goes to the front of the frame to drain fuel) whenever I leave the fuel selector valve in the'on' position after shutdown. But that's not all. If the fuel selector valve is all the way open,I have noticed draining fuel (sometimes) from that overflow hose when I'm at astop (with the engine running). I don't really know if it drains when I'm driving.I don't think so because mympg seems about normal. One way that I have solved thisproblem for now is to place the fuel selector valve in the 'on' position but not all the way'on'. Sort of half way between off an on. I haven't noticed any fuel leaking while the engine is running when I leave the fuel selectorvalve halfway. It will leak after shutdown though so I turn it off all the way.
So maybe that is a factor in high speed performance weirdness.
What do you think? Thanks for any help.
There is the possibility that there is an air leak in the inlet manifold O rings since I had the carb off with the inlet manifold over the winter. That's one thing that I'll check.
Also, you mentioned the float. It runs really great except for the times when I have weird high speed performance. But you mentioned that if the float was out of adjustment (too high), then fuel would leak. If the float was adjusted too low then I would lose power in turns. I don't lose any power in the turns. But here is something that may be a factor. Fuel will leak from the overflow hose (I'm talking about the littlehose that comes from the float and goes to the front of the frame to drain fuel) whenever I leave the fuel selector valve in the'on' position after shutdown. But that's not all. If the fuel selector valve is all the way open,I have noticed draining fuel (sometimes) from that overflow hose when I'm at astop (with the engine running). I don't really know if it drains when I'm driving.I don't think so because mympg seems about normal. One way that I have solved thisproblem for now is to place the fuel selector valve in the 'on' position but not all the way'on'. Sort of half way between off an on. I haven't noticed any fuel leaking while the engine is running when I leave the fuel selectorvalve halfway. It will leak after shutdown though so I turn it off all the way.
So maybe that is a factor in high speed performance weirdness.
What do you think? Thanks for any help.
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
RE: high speed performance weirdness
You have either or both:
The float level is set too high...and/or,
the float needle and seat are worn and need replacement.
It could be either.
Pull the float bowl and carb off to check the float level. If that is set correctly, but a new needle and seat and install. Of course you will have to set the float level again with the new parts.
The bike should never leak fuel anywhere, running or stopped. The float raises and seats the needle in place to cut off all fuel flow. If the float is too high, the fuel level rises to the point it simply runs out the overflow tube.
If the needle fails to seat, then the same thing happens and the fuel runs out.
At this time you should also make sure the manifold O rings have not slipped out of position causing an air leak. The popping in the pipes makes me almost sure there is an air leak..............pg
The float level is set too high...and/or,
the float needle and seat are worn and need replacement.
It could be either.
Pull the float bowl and carb off to check the float level. If that is set correctly, but a new needle and seat and install. Of course you will have to set the float level again with the new parts.
The bike should never leak fuel anywhere, running or stopped. The float raises and seats the needle in place to cut off all fuel flow. If the float is too high, the fuel level rises to the point it simply runs out the overflow tube.
If the needle fails to seat, then the same thing happens and the fuel runs out.
At this time you should also make sure the manifold O rings have not slipped out of position causing an air leak. The popping in the pipes makes me almost sure there is an air leak..............pg
Thread Starter
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Cruiser
Joined: Jan 2007
Posts: 209
Likes: 0
From: Fort Campbell, KY
RE: high speed performance weirdness
Do you think an air leak in the inlet manifold O rings could lead to a hole being burnt in a piston?
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Thread Starter
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Cruiser
Joined: Jan 2007
Posts: 209
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From: Fort Campbell, KY
RE: high speed performance weirdness
ORIGINAL: piniongear
Pull the float bowl and carb off to check the float level. If that is set correctly, but a new needle and seat and install. Of course you will have to set the float level again with the new parts.
Pull the float bowl and carb off to check the float level. If that is set correctly, but a new needle and seat and install. Of course you will have to set the float level again with the new parts.
I'll get to reading in my factory service manual and see what is involved in checking on that float level.
Thanks a lot.
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Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
RE: high speed performance weirdness
Yes, I am certain it is one or both of those conditions. It may be possible that the level is just barely above the maximum heigth, so when the engine is running and sucking fuel out of the float bowl nothing goes into the overflow until you shut off the engine. After that the fuel level, being just a tad high, drops fuel into the overflow tube. That would be on the ragged edge of float level adjustment.
Truth be known, it is better to have the level set a hair lower than recommended (the float is set lower so it closes before the float bowl fully fills) than a hair over. Being over will spill fuel into the overflow, especially when the engine (and fuel in the bowl) has warmed up to operating temperature.
Sounds like you have a handle on it.
With the carb off the manifold.....install the manifold to the engine. This allows you to stick your finger(s) into the inside manifold to feel the inside surface(s) of the O rings. As you tighten the clamps you will easily feel if the O rings start to slide out of position between the heads and the manifold.
If they do shift, undo everything and start over again from scratch.
Look at the air gaps between each manifold edge and each head, with the O rings not in place. Is each reasonably parallel? If not, loosen the 4 base nuts on the offending cylinder and use a plastic mallet to whack the cylinder into a better fit. Retighten the base nuts and then install the manifold.
I have had to redo this several times to get the rings to stay put while the clamps are fully tightened. Things are correct when the rings have not moved, the clamps are tight, and the inside surface of both rings are even all around, using you finger to judge this.
Then install the carb and you should be set with no further problems with air leaks........pg
Truth be known, it is better to have the level set a hair lower than recommended (the float is set lower so it closes before the float bowl fully fills) than a hair over. Being over will spill fuel into the overflow, especially when the engine (and fuel in the bowl) has warmed up to operating temperature.
Sounds like you have a handle on it.
With the carb off the manifold.....install the manifold to the engine. This allows you to stick your finger(s) into the inside manifold to feel the inside surface(s) of the O rings. As you tighten the clamps you will easily feel if the O rings start to slide out of position between the heads and the manifold.
If they do shift, undo everything and start over again from scratch.
Look at the air gaps between each manifold edge and each head, with the O rings not in place. Is each reasonably parallel? If not, loosen the 4 base nuts on the offending cylinder and use a plastic mallet to whack the cylinder into a better fit. Retighten the base nuts and then install the manifold.
I have had to redo this several times to get the rings to stay put while the clamps are fully tightened. Things are correct when the rings have not moved, the clamps are tight, and the inside surface of both rings are even all around, using you finger to judge this.
Then install the carb and you should be set with no further problems with air leaks........pg
Thread Starter
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Cruiser
Joined: Jan 2007
Posts: 209
Likes: 0
From: Fort Campbell, KY
RE: high speed performance weirdness
I'm thinking that the float is too high because of the overflow. Like I said, the carb is fresh off a rebuild so it should not have any wear where it should make a difference here.
I removed the float bowl to adjust the float. My factory service manual says to adjust float mounting tabs for correct fuel level. I don't see any mounting tabs. I don't know what it's talking about.
Thanks for any help.
[IMG]local://upfiles/23810/8251E50D048F4E10AB4E8CFE2C8D330A.jpg[/IMG]
[IMG]local://upfiles/23810/EDC53563DC3045E38C9AA7698ED1D005.jpg[/IMG]
[IMG]local://upfiles/23810/5818FF49EF084A4FBBD407C8F7E32FD0.jpg[/IMG]
I removed the float bowl to adjust the float. My factory service manual says to adjust float mounting tabs for correct fuel level. I don't see any mounting tabs. I don't know what it's talking about.
Thanks for any help.
[IMG]local://upfiles/23810/8251E50D048F4E10AB4E8CFE2C8D330A.jpg[/IMG]
[IMG]local://upfiles/23810/EDC53563DC3045E38C9AA7698ED1D005.jpg[/IMG]
[IMG]local://upfiles/23810/5818FF49EF084A4FBBD407C8F7E32FD0.jpg[/IMG]