80 Liquifre

JDGuy · Post by **JDGuy** » Tue Feb 21, 2006 2:37 pm

Hi:
I would really appreciate some help on this one. I am restoring the sled and have it in really good condition after a lot $ except for the following situation: It starts hard at cold start. Doesn't like much if any choke, cold engine, 35 degree garage temperature, air box on, clean box and inlet screen. After some pull rope work, it cold starts but it will not idle above 1000 RPM. Any SLIGHT touch of the choke or throttle at this speed kills the engine. If left alone to run at 1000 RPM it will warm up, and the idle speed picks up and when it is fully warm (160 degree water temp via new Westach gauge & confirmed with lazer spot gun), it starts bumping up against the speed limiter at just under 4000 RPM. This occurs after it is warm enough to burp the throttle. I thought maybe the slides were sticking but that was not the case. Back off the idle screws to 3200 RPM or so and it purrs like a kitten. Disconnecting the speed limiter seems to have no effect. Runs strong under load, can feel a small bit of front end lift at 3/4 throttle burst. Carbs and oil pump synchronized, choke plunger seating surfaces good, choke set to 1.25 inch right and 1.20 inch left per manual, plently of free play. After a night of cold soak, it seems to like a little more (1/4 turn) initial idle screw setting to start, then again, it runs up to the speed limiter when warm at the higher idle screw setting, sort of a catch 22.

The carbs have been cleaned and recleaned, totally dismantled, and soaked for more than a week in some good $20/gallon cleaner, then aerosol carb cleaner sprayed through all passages, and then blew out with 100 psi air. NEW 40 pilot jets installed per spec, new little 0-rings that seat in the bowl. Main and power jets bores are shinny clean via 10X magnification glass. Air screws initially set at recommended 1.5 turns open and adjusted to 2 turns open which yielded a smoother idle at warm engine. Both cylinders read about 105 psi compression with a good Sun Automotive gauge and cold engine. Manual says 100 psi minimum for used engine. It is a used engine. Bores look ok as viewed through intake and exhaust ports. The odometer says 1700 miles but being it was purchased used I cannot be sure of that. Coil and CDI are either NOS or more likely, the originals. Spark appears good via home made spark tester (plug with ground strap removed, alligator clip screwed to thread area). No apparent mouse nests in the muffler or high speed operation would be effected.

I am baffled by this one. I normally can figure things out, but not this one. I would sure appreciate your suggestions!!!!

JDGuy · Post by **JDGuy** » Tue Feb 21, 2006 3:59 pm

Thanks Rich, no I have not. I have had everthing apart but the engine. I have not messed with the stator or anything under the flywheel, but of course, that does not mean it is correct.

Post by **guitardude081** » Tue Feb 21, 2006 5:51 pm

You can unplug the rev limiter.
~Jack

JDGuy · Post by **JDGuy** » Tue Feb 21, 2006 9:12 pm

Rich:

I found the timing mark on the stator at 3 o'clock through a hole in the flywheel per your post of a couple of months ago (align stator, don't use timing light, etc). But my old eyes are failing me in locating the adjacent boss on the crankcase unless that boss is a thin tab about .060 thick and running in the vertical direction. The stator index mark is about a 1/4 inch below and parallel with the crankcase split line. If I read your post correctly, that if off timing, correct? Any additional explanation for "dummies" that you could give me would be great.

Thanks!!!

liquifirejason · Post by **liquifirejason** » Tue Feb 21, 2006 9:28 pm

what size pilot jets are in it? dont screw the idle screw way in. my liquifire wouldnt run at low rpm either. i had to small of pilot jet in it. but, it wasnt stock motor....

JDGuy · Post by **JDGuy** » Wed Feb 22, 2006 9:58 am

Rich:

Found the picture in the TM you mentioned. Timing appears to be right on the mark. Still trying to find source of the problem.
Thanks for the help.

quadfamily · Post by **quadfamily** » Fri Feb 24, 2006 3:19 pm

Is 105 psi really good enough for the compression? I know my Sportfore and Trailfire are around 150-160 on fresh pistons and rings. Just asking.........

JDGuy · Post by **JDGuy** » Fri Feb 24, 2006 5:22 pm

Quadfamily:

Yes, compression is at low end, it is apparently a very used motor, most likely a lot more miles than the odometer shows. Tech Manual says 120 to 140 psi, 100 minimum for used engined. I am bumping the minimum.

I "think" I have my problem fixed based on only a couple of cold start/warmups. Too soon to report it fixed. If it continues to be "fixed". I will report what the problem was when I am certain of it.

Current outside temp is 35 degrees and no snow. Some in forecast. TBD

JDGuy · Post by **JDGuy** » Sun Feb 26, 2006 5:23 pm

Starts first/second pull, idles right up to 3000 RPM after new choke plungers. Photo below is attempt to show center of plungers that apparently (?) extruded into orifice from years of setting, although still fairly soft. Extruded portion highlighted with silver pencil. Sorry it is out of focus, my camera does not have close focal length.