peak engine rpm on 81 liquifire?

qwerty · Post by **qwerty** » Wed Feb 20, 2008 7:48 pm

liquifire pulls to 7000 across the lake. wont rev higher no matter what. seems to attain this rpm from half throttle to full.
engine feels very peaky but wont go faster than 7000. is this correct? or should it rev more?

Liquifire 4/6 · Post by **Liquifire 4/6** » Thu Feb 21, 2008 12:32 am

Mine always held a solid 8100 whenever the drive clutch was in decent shape. Seven grand is way too low. It likely isn't even kicking out 40 hp at that RPM. I'd look into your clutches for wear.

Mr. Deere · Post by **Mr. Deere** » Thu Feb 21, 2008 4:27 pm

Mine doesn't go above 6000. Or 60 in the air fixed the leak and with the snow coming tomorrow will see how she does. BOB

deere guy · Post by **deere guy** » Sun Feb 24, 2008 3:55 pm

Could be your tach is not accurate. Espescially if the machine runs good and seems to have good power. Could also try unplugging the rev limiter and see if that helps.

JDT · Post by **JDT** » Sun Feb 24, 2008 4:07 pm

The rev limiter is not the problem.

When it kicks in it just shuts the ignition off.

If it were acting up at the high rpm it would be jerky and the engine would be backfiring.

...........

I would look at clutching or a bad CDI.

The CDI may not be able supply spark above 6000.

But checking the tach is a good idea also.
Just switch it out with another sled and see what it does than.

kenwaters · Post by **kenwaters** » Fri Feb 29, 2008 10:37 am

Qwerty,

Check your clutching, it sounds like you may have a trailfire set of weights and primary spring. Beyond that, check the obvious, obstructions in the airbox/exhaust.

Mr. Deere · Post by **Mr. Deere** » Fri Feb 29, 2008 10:55 am

Is it possible to have a CDI go out above a certain RPM. Would unplugging the main harness help at all. QWERTY you find out what was the matter with yours yet. BOB

qwerty · Post by **qwerty** » Sun Mar 02, 2008 12:34 am

as for clutching, i think it is in order. engagement is 45+. marked both pulleys and they are shifting all the way. sled wont rev out even with the track raised.

i found the ground wire on the coils was broken, when i was trying a new (used) coil. did not help.

i have monkey'd with the timing, advanced-retarded, no improvement just harder to start.

i removed the rubber hose on the airbox, and loosened the box where it attaches to the carbs. this netted me an inconsistant 7300+ rpm. this test in conjunction with the piston wash is telling me im to rich on the jetting.

the sled starts when cold,runs (great to 7000) for about 15 minutes then (for lack of a better term) craps out and dies. last time it did this i gave the primer a couple of pumps and it cleared up briefly. my latest theory is that the fuel pump is bad, not keeping the bowls full and not supplying enough fuel at high rpm. untill it gives out completely and quits.
it also seems sensitive to heat especially idleing when warm. a 20 second pause will foul a plug.

1-my next plan of attack will be to inspect the pulse line, remove the pump and inspect/clean/repair or replace.
2-set the timing back to stock.
3-order some jets and play around with that.

as a side note the jugs were borderline when i put it together, it is showing 100 psi on both sides when cold.

malone · Post by **malone** » Sun Mar 02, 2008 12:56 am

my 81 liquifire 440 which I rode today, when I put in premium it will go up 9000 I would bet it has even gone higher than thet. and I have never even heard of a rev limiter? does my 81 440 have one? Does my 76 440 motor have one? and how would I unhook it. or should I leave it alone.

Mr. Deere · Post by **Mr. Deere** » Sun Mar 02, 2008 12:01 pm

Yes the 81 does Malone and It keeps the motor from going over 9000. Leave it alone unless you want to replace a motor. BOB

malone · Post by **malone** » Sun Mar 02, 2008 2:03 pm

ok thanks, but does the 76 440 have a rev limmiter?

JDXspec · Post by **JDXspec** » Sun Mar 02, 2008 2:09 pm

A 76 LF does not have a rev limiter

qwerty · Post by **qwerty** » Tue Mar 04, 2008 12:29 am

i just thought of someting else. it may be possible that the vent tube is pinched somewhere, creating a vaccume, causing the sled to run for a while and then quit. also it may be affecting the fuel pumps ability to work properly.

Mr. Deere · Post by **Mr. Deere** » Tue Mar 04, 2008 10:01 am

Yes if your fuel pump is clogged or has a hole in the diaphragm it will do the same. I have cleaned and re assembled my pump several times maybe this summer I will replace the guts. BOB

Post by **ICCSF 108** » Tue Mar 04, 2008 12:09 pm

Mr. Deere wrote: I have cleaned and re assembled my pump several times maybe this summer I will replace the guts. BOB

Bob, Why? Is dirt or some foreign material getting in it??? or do you just want the practice?? wouldn't it be easier to make sure the fuel filters are clean??

Kenny