FT9.9 AE X Cylinder head removal

[panasonic]

The head was 5 thou out, high in the centre, had it resurfaced for £30 and finally got it all back together.
Motor started instantly and warmed up nicely, good water flow and no overheating but not run under load. Revs up nicely but misfires when held at high revs.
Also disappointed that compression only 115psi although same on both cylinders.

Are you hitting the Rev limiter?

[99yam40]

do race saws have more than one cylinder?
never even looked at one myself, but watched some on TV in the past/

the blowers are loaded as much as they were designed for with the fan

but weed eaters are designed to hit weeds and not just spin the line

yes 4 strokes are different than 2 strokes
forgot this was a 4 stroke thread

what vacation?

[pstephens46]

I thought you were headed out to ranch for another brush clearing exercise.

[TownsendsFJR1300]

What do you mean you only hit the Rev limiter once? That bike will wheelie starting at 50 mph....they are rocket ships.

Rev limiter kicks in at about 14,500, 15,000 RPM's (screaming).

It's an upright sitting bike, regular handle bars-actually with bar risers/set backs. (I don't do the lay down thing).

The engine thou is a slightly de-tuned R6 (GO-fast bike) engine.

Hit the rev limiter once in second gear, about 90 MPH (6 speed). First gear picks up the front wheel (don't like to do wheelies either, it hurts if you screw up) at about 8,000 RPM.

The engine is very tame under 5K, 6K and up, (with aftermarket pipes), it "wakes up" and is a very different bike, "coming on the pipe". It does sound like a 1000cc go fast bike past that 6k RPM.

About 47 MPG around town and usually 95% of the time, under 6K RPM's.

2007 model, about 25,000 miles now..

[99yam40]

I thought you were headed out to ranch for another brush clearing exercise.

Not yet, but will real soon
My church was having a fall festival that I helped set up and take down yesterday.
will finish up the clean up this afternoon

[cleddau1]

C'mon boys do you really believe I would rev an engine to max unloaded, especially one I had just partially rebuilt? However I should have been more specific. When held at just above 2000rpm it misfires. The reason was that when refurbishing the head I had put in some old spark plugs to protect the threads. New spark plugs and some adjustment to mixture and engine is fine.
Any comments on the compression?
Many thanks for the all the advice and encouragement.
Big tides at 7.4 metre range due to proximity of moon so yesterday used human power to kayak the Eastern Cleddau as far as the Weir. Favourable tidal stream both ways so mostly doing over 4kn, almost as fast as my sailboat........

[99yam40]

what was the compression before you took it apart?

115 sounds good for 2 stroke.
but I thought that the 4 strokes had more compression than 2 strokes,

but with all of that carbon in combustion chambers, maybe the rings are carboned up too
'
has anyone here run a compression check on a F9.9 to give him a comparison?

Tides down here are just a couple of feet.
half the land down here would go under if we had 7 meters

I bought a training kite for kite surfing, thought I could use it to pull me around in my kayak.
no good way to launch it on the water.
so it is just a play toy when I can find open areas and wind

[cleddau1]

Update:
following head rebuild as above engine was used all last season and ran well; starts instantly cold or hot but when throttling back to idle tends to stall; immediately restarts; idle speed is set as per manual. Any advice welcome.

[pstephens46]

No carbs here so maybe no help. Surprised Yam or someone hasn’t commented. Guys, what is the pot? device on carb that poots a little more fuel into carb when suddenly pulling back on throttle? Just a faint memory as the older conversations didn’t apply to me. Not sure his carb has the thing.

[walleye1]

Dash pot isn't working

[99yam40]

cled, did you happen to run another compression test after the motor had been run for awhile?
Just curious if it came up.

Walleye has the best answer on the dying
throttle plates closing to far too fast

[boscoe99]

No carbs here so maybe no help. Surprised Yam or someone hasn’t commented. Guys, what is the pot? device on carb that poots a little more fuel into carb when suddenly pulling back on throttle? Just a faint memory as the older conversations didn’t apply to me. Not sure his carb has the thing.

It is a device that slows down the rate of closure for the throttle plates.

[pstephens46]

It is a device that slows down the rate of closure for the throttle plates.

If you tell me repeatedly there is a good chance I may remember. Hey, I was close.

[boscoe99]

A visualization may help the memory.

Electronic throttles and ISC valves act as dashpots when there is not one physically on the motor.

[cleddau1]

Thanks for replies, will run another compression test when I recommission engine after winter lay up. Premature throttle valve closure sounds a logical explanation for my problem. However there is nothing on the engine looking like the dashpot on the triple carb diagram and as you all know this a single carb engine. Is there any other adjustment on the carb that alters the rate of throttle valve closure?