Topic: Need ideas on 78 750F

[6adan]

 I bought this bike not running but with engine not locked up. I cleaned carbs and got it running somewhat, it will not idle so checked compression on #1&4 and 1 had 30 psi and 4 and 60. I was going to do a leek down test but I have a lot of air coming out if the intake. I looked down the intake and can see no rust on valve. This is with #1 on TDC and even with adjuster loose. Is my next step pulling the head? I am thing so but thought I would get the wisdom here first.

Thanks Dannie

[Don R]

Check the rockers for proper adjustment. I had one that had carbon fouled valves from a plugged exhaust. They did clean up, Maybe some marvell mystery oil? I think it's not good on the clutches but cleans carbon. Or some seafoam in the gas and oil.
 Look at the rockers through the adjuster ports to check things.
 If it's clattering a lot there may be something broken. Just guessing at this point.

[Airborne 82nd]

If you can get it on the road do so. Mine did the same plus smoked a lot after 100 miles or so with a double dose of seafoam all cleared up then I went back and did a 3K.

[DWS]

Check for leaks around your boots, mine where leaking pretty bad.

[ekpent]

How many miles is it showing on the odometer and has it sat outside. Any pictures ?

[Airborne 82nd]

Check for leaks around your boots, mine where leaking pretty bad.

How would this effect compression with the rockers loose ?

[6adan]

I have adjusted the valves and the timing, it has 27000 mi. has not sat outside.

[Old Scrambler]

When the valves/rockers are set and the cam-chain is adjusted, assuming all else is good, the motor should run and most of the compression will return. I would expect smoke on start-up and burning some oil due to leaking valve seals and worn valve-guides. Very typical for the F2-3 motors. As the wear gets worse, the valves tend to show dimples from the rocker-adjusters.

Do some hunting on these pages for more info..............

[DWS]

You said it did not idle to well. Sometimes that's the boots leaking.
How did you check compression?
Cold
Hot
Wet

[6adan]

Thanks everyone. DWS it will not idle at all, I did the compression check cold and after the first test I did add a little oil and it came up a little but not enough to make it run as it should. Like I said I am getting air past the intake valve when at TDC and valves closed. It dose not run good enough to ride on the road. I did adjust the valves before I started all of this.

[DWS]

have you rebuilt the carb yet? the slow jets that have to be pulled out instead of unscrewed that's where the problem was on mine
if not that would be next.
plus the small hose next to the fuel intake line needs to be open to the air, see the hose with the red plug in it? should not be plugged. mine was for some reason.
have you done the clear hose level test on the bowls?

[lucky]

have you rebuilt the carb yet? the slow jets that have to be pulled out instead of unscrewed that's where the problem was on mine
if not that would be next.
plus the small hose next to the fuel intake line needs to be open to the air, see the hose with the red plug in it? should not be plugged. mine was for some reason.
have you done the clear hose level test on the bowls?

That bottom photo is trouble.
The fuel CANNOT be above the overflow tube in the float bowl! Look at the overflow tube.
It is NOT level with the top of the float bowl. So you know that setting the float level with the top of the float bowl cannot be  correct.

Set the float level like the book shows you. That is all you have to do. End of story.