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Power Cold/Hot Question

  • Thread starter Thread starter DMPLATT
  • Start date Start date
D

DMPLATT

Guest
Just a curious question that I may already know the answer to.

My 750E runs great. However, during this heatwave of a summer I've noticed something.

I'm a daily commuter. In the Morning there is a couple stretches that I can open her up. She runs Awesome and Pulls hard. On the way home, I usually can't open her up til almost home and she's getting hot by then. Temp gage is around 210deg.

So, today I had the chance on the way home and here is what happened that doesn't happen when she's cooler.
1. She wasn't pulling as strong.
2. Once in a while on take off, or rolling back on the throttle I can hear a slight knocking noise. Now this Knocking could be a Pinging, similar to a car that is using low octane gas or the timing is off slightly. My old Tempo did this when the AC was on and I tried to accelerate. I know it's not serious, just a slight knocking noise.

Another symptom is that I use about 1/2 to 3/4 qt. oil in about 800 miles. I never see any smoke, plus I no longer leak anything (new oil lines a while back).

So, is it possible that I'm losing power when she's hot due to Valve seals or something to do with the valves?

Thanks.
 
I think it's more probable that you are running a bit lean, any mod's, ie aftermarket muffler, K&N airfilter.
If not check for a vacumn leak between the carb's and the head, that could be your prob Dave.
 
gspaul said:
I think it's more probable that you are running a bit lean, any mod's, ie aftermarket muffler, K&N airfilter.
If not check for a vacumn leak between the carb's and the head, that could be your prob Dave.
Click to expand...

Well, this bike has always been a tad lean. Even with my new Supertrapp tunable exhaust. Maybe I should play with that some more?
The PO or whoever, put on a 4-1, but no jets or pods. I just put on a new Supertrapp 4-1.
As far as the vacuum leak, hmm. I AM having trouble getting my carbs to synch. I can get them close, but not perfect. I will check with WD 40.

Thanks guys.
 
All motors lose a little power when it's hot out. Even when jetted well and all other things are set correctly, hotter temps will cause some loss of power. Hotter temps make the mixture richer. All motors are effected this way. But your pinging problem isn't related to the normal richening that occurs on hotter days.
As for your pinging, if that's what it is, your aftermarket exhaust could cause it, all by itself. If the ignition timing is off a little (advanced), that will worsen it. If the valve clearances are too tight, that will result in some power loss. Then there's lower octane gas...dirty carbs...air filter...partially blocked gas tank venting...all can contribute to pinging, which is a lean condition. The lean condition allows combustion to happen unevenly and before the piston reaches the power stroke. The piston is trying to fight it's way up against the early combustion, causing the ping/knock.
I don't know how well that pipe increases flow, but you should at least go up a full size on the main jets. Get plug reads at full throttle.
Then get reads at 1/3 throttle to see how the jet needle mixture is.
An additional 1/2 turn out on the mixture screws will help. Maybe a full turn. Keep a record so you can put them back if you want.
A carb vacuum synch should be done as basic maintenance too, in addition to the above.
 
power

power

If every thing is adjusted right then you maybe getting the ping/knock from carbon deposits, that are getting hot and causeing pre-ignition when the engine is running in the hotter weather, in witch case you have to pull the head and decarbon it, you can damage the engine if it is bad enough and may be if you are wearing a full face helmet, covering up some of the noise
 
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