Won't Run once it's warmed up??? '76 Liquifire

[thevintagesnowmobile]

Hey guys,
I just picked up my '76 Liquifire 440 a couple weeks ago. I have taken the carbs apart and cleaned everything out, I put new spark plugs in, put fresh gas/oil in and replaced the fuel hoses etc.... I put everything back together and my sled runs AMAZING!! Sounds great, tons of power, runs smooth. BUT once i've driven it for 5-10 minutes and it gets warmed up it starts bogging really bad, to the point that it won't even drive. It idles just fine and starts right up but once you give it gas to make it drive it bogs down and won't go anywhere. Please help!!! I'm trying to get this sled up & running for christmas break. thanks!

[ICCSF 108]

What alt. are you & what Main Jets?

Kenny

[thevintagesnowmobile]

What alt. are you & what Main Jets?

Kenny

4465 ft. I don't remember the main jet size but I can take it apart again and look if you need to know. I figured the jetting should be fine because I bought the sled from the original owner that has always ridden it here where I live. (Logan, UT)

I forgot to mention before that I tightened up the track a little. I don't think I overtightened it but could that cause the problem too? Maybe it's overtightened causing the engine to bog down because it can't spin it? How do you know how tight to make your track?

[harleysportster]

Spence,
Does it run better when it is cold?
Remove the choke plungers and inspect the rubber seals. If the rubber is worn, it causes a RICH carb condition.
Check the free-play of the choke cables, there should be about 1/16 in. slack at the adjusters, when the choke is off.
Check the condition of the fuel filters.
Not to sound repetitive but the crank seals could be worn.
Here is a link to an online service manual. It is a large file which could take some time to load. The track info will be in there. I would set the track at 1/4 to 3/8 in but watch and listen for track ratcheting of the drive sprokets.
http://www.vintagesnow.com/John_Deere_f ... yclone.pdf

[moontree]

i have experienced the same "problem" with my 77 Liquifire. being Liquid cooled they run cool when you don't work em'. after riding with other novelty rides (ie slow pokes) for awhile it would bog and stall, yet start back up. so i was advised. GO FAST!!!!! make a couple hot laps at 45mph+ then see if it clears up. you gotta get the temp up for awhile to "un foul" the plugs

[lwb140]

are you loosing spark ? could be your high rpm coil on your stator ?? id get an inline ignition tester so you can watch the spark . how much compression does it have ??

[harleysportster]

i have experienced the same "problem" with my 77 Liquifire. being Liquid cooled they run cool when you don't work em'. after riding with other novelty rides (ie slow pokes) for awhile it would bog and stall, yet start back up. so i was advised. GO FAST!!!!! make a couple hot laps at 45mph+ then see if it clears up. you gotta get the temp up for awhile to "un foul" the plugs

No disrespect but I dissagree. If the engine starts to bog down and die, I would see if the plugs are fouling which would indicate the jets were to rich.
lwb140 brings up another good point which the 76 Cyclones and Liquifires are know for. The ignition system failing as the engine become warmed up.

[moontree]

so maybe mine runs to "fat" as well. is there a suggestion for what jets to start with? 650' elevation.

[thevintagesnowmobile]

Spence,
Does it run better when it is cold?
Remove the choke plungers and inspect the rubber seals. If the rubber is worn, it causes a RICH carb condition.
Check the free-play of the choke cables, there should be about 1/16 in. slack at the adjusters, when the choke is off.
Check the condition of the fuel filters.
Not to sound repetitive but the crank seals could be worn.
Here is a link to an online service manual. It is a large file which could take some time to load. The track info will be in there. I would set the track at 1/4 to 3/8 in but watch and listen for track ratcheting of the drive sprokets.
http://www.vintagesnow.com/John_Deere_f ... yclone.pdf

Yes it seems to run fine for the first 5-10 minutes and then when it gets warmed up it doesn't want to run. It will start and idle just fine but if I give it gas to go it just bogs down and won't move. I will check the choke plungers and seals. I will also do the crank seal test with some starting fluid. I'm pulling it back in the garage tomorrow and I'll let y'all know what I find. Thanks for the info.

[thevintagesnowmobile]

are you loosing spark ? could be your high rpm coil on your stator ?? id get an inline ignition tester so you can watch the spark . how much compression does it have ??

I don't know if I'm losing spark. I will have to test that, I also am not sure on the compression. I don't have all the tools but I will get one and test that as well either tomorrow or tuesday and give y'all an update. thanks for the info.

[thevintagesnowmobile]

Alright... This morning I pulled the JD back into the garage and checked some of the things you guys have suggested. The choke cables and plungers seems to be functioning fine, seals also look fine on those. I did the crankshaft seal test with some wd40 and the motor revved up when sprayed on there. Would that bad seal cause my sled to run the way it has been? Is replacing that seal a fairly easy project? From what I can tell I just need to pull the clutch off and undo a few bolts there around the crankshaft?

Also I was planning on replacing the ignition coils while I was at it, i noticed places are selling primary ignition coils and secondary ignition coils. I pulled the cover off and I can see the secondary coils but I don't see the primary. If it's not obvious to y'all I'm not much of a mechanic so I was wondering if my sled has both primary and secondary? If so, where is the primary, and do both need to be replaced?

[harleysportster]

Alright... This morning I pulled the JD back into the garage and checked some of the things you guys have suggested. The choke cables and plungers seems to be functioning fine, seals also look fine on those. I did the crankshaft seal test with some wd40 and the motor revved up when sprayed on there. Would that bad seal cause my sled to run the way it has been? Is replacing that seal a fairly easy project? From what I can tell I just need to pull the clutch off and undo a few bolts there around the crankshaft?

Also I was planning on replacing the ignition coils while I was at it, i noticed places are selling primary ignition coils and secondary ignition coils. I pulled the cover off and I can see the secondary coils but I don't see the primary. If it's not obvious to y'all I'm not much of a mechanic so I was wondering if my sled has both primary and secondary? If so, where is the primary, and do both need to be replaced?

Spence,
The spray test indicates a bad seal. I would replace both outer seals at the same time. They are not hard, just time comsuming since you have a Liquifire. It is much easier to do the job with the engine on the bench.
Special Tools needed:
Clutch puller
Flywheel / steering wheel puller
Torque wrench.
The only coils on your engine are on the outside mounted to the back-side of the cylinder jug. There is no need to replace them if they test good and work. I would clean the rust off the terminals and check the grounds.
You can test the external ignition coils by using a ohm meter.
To test the coil, measure the ohms between the primary stud terminal and the high voltage spark lead and between the high voltage spark lead and the small grounding wire. I believe 100-300 ohms is an acceptable range. Also test between the lead to the ground connection to the primary terminal of the coil...it would be from .1 to . 5 ohms.
While you have the engine out, check the Stator.
http://www.jdsleds.com/community/viewto ... ?f=5&t=289
Again, preview all the repairs in the service manual.

[harleysportster]

so maybe mine runs to "fat" as well. is there a suggestion for what jets to start with? 650' elevation.

http://www.jdsleds.com/community/viewto ... ?f=5&t=368

[HoosierDeereMan]

Just a word of advise on removing those crank seals. The crankshaft bearings are right behind the seals. Becareful of driving a screwdriver or punch too far into the seal or you can damage the bearing. I would advise using a seal puller. They are a pretty cheap item at any auto parts store. You can make a starter hole with a screwdriver and then use the the seal puller to pry it out.

Also the sharp edges on the woodruff key that aligns the flywheel to the crank are tough on new seals. I would remove the key and use STP oil treatment on the crank and the lip of the seal before installing them. It will help keep from damaging them when installed. It will also help lube the seal until your 2-cycle oil can get to it. Make sure you wipe off the excess STP after the seals are installed.

Both of these were learning experieneces for me when I did this.

Troy

[harleysportster]

Good points Troy. It is very easy to leave out details that you assume everybody knows.