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

[lwb140]

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?

i put crank seals in iphones old 79 trailfire tonight it was going all kinds of goofy things but all in all it ran pretty well but the pto side seal was actually in 3 peices the inner lip and spring were detatched from the seal it runs much much better now . crank seals will make a sled to everything from make the fuel pump not work to suck air and run lean wade

[FireRider34]

My 76 liquidfire 340 does the same thinng it ran fine last year and as soon as i replaced the throttle cable it never ran right and I have no clue how to adjust my carbs any have some advice?

[harleysportster]

My 76 liquidfire 340 does the same thinng it ran fine last year and as soon as i replaced the throttle cable it never ran right and I have no clue how to adjust my carbs any have some advice?

-Remove the airbox
-Loosen both carb cables
-Loosen the idle screws ,place a finger on a slide then turn in the screw until the screw just touches the slide, then 3 complete turns, setting both carbs the same.
-Tie the throttle handle back against the handlebar in the full-on position
-Use a mirror and look inside the carbs and ajust the cables so the inner edge of the silde near the reeds is just flush with the top side of the bore.
-Set both carbs the same way
-Release throttle, warm up engine and adjust idle move both idle screws at the same time.
It's all in here...
http://www.vintagesnow.com/John_Deere_f ... yclone.pdf

[FireRider34]

Well thank you very much, i got it just perfect I realy enjoy all the help I get from you guys.

[74 jdx8]

father had a simmiler problem with his 1980 liquifire. Ended up the fuel pump was the problem. Dont buy the re-build kit, just buy the whole fuel pump, its the same price.

[thevintagesnowmobile]

I've taken a few weeks off from the JD due to the holidays and my kids got sick..... I busted it back out and here's the latest:

Based off of the comments I've had on this post and a lot of research online I've decided replacing the crank seal is the next step in troubleshooting this issue. These are the reasons why;
- My sled tends to run awesome for the first 5 minutes and then it bogs down and barely idles.
- It seems to run better in mid-high rpm range, not so much the bottom end.
- It seems to struggle sucking new fuel in.
- When I spray starting fluid into the airbox it runs great, when i spray starting fluid around the crank it revs up.

In my research, all of these symptoms are related to the crank seal going out. I am posting all of this information for my own records but also for anyone that may run into the same problem down the road. I don't have a clutch puller so i got a hold of a small engine repair shop here in my area that pulled it off for me and is replacing the seal. It should be done tomorrow and then i'll post an update on how it performs.

[thevintagesnowmobile]

Great News! Replacing the crank seal fixed the issue i've been having. I just picked it up from the small engine repair shop today and they had it all ready to go for me. I've been riding it around for the past 20 minutes or so and so far there hasn't been an issue. In the next few days I should get a chance to ride it around longer and put it to the test. I'll post an update and some more pictures. I'm surprised how much fun I'm having riding this old liquifire, it actually has some power! Thank you for all the comments and suggestions with this problem.

[JD_Sledder68]

Can the crank seal on the mag side be changed out without splitting the case, as well?

[400brian]

Yes, I just did it on my '78. You'll have to pull the flywheel and remove the stator. Mark the position of the timing ring, then remove it to gain access to the seal.

[thevintagesnowmobile]

Here it is two years later and I'm still bringing this topic back up.... Snow will be flying soon and I'd like to get my Liquifire running good once and for all!
Replacing my crank seals did help, and the sled does run great for 10-15 minutes now, but again after it gets hot i'm losing spark on one cylinder and it won't run worth a crap. I've replaced the ignition coils and that didn't fix it so the only thing (from what i've read) that I can try now is to replace the stator. It seems like this model of JD is notorious for having stator issues? Where can I get a new stator? Or can I fix the one I have? Let me know what you guys think.

[HoosierDeereMan]

Spence,

Try http://www.cdibox.com/

This is the website for Hewtech. He sells rewound stators or can rewind your stator. He also sells CDI boxes. I highly recommend both. I've installed his rewound stators on my JDX8 and 340/S. Scott is very helpful.

Over time the heat from the engine breaks down the insulation on the stator. It may cause the lighting circuit to fail or in your case the ignition to lose spark.

Troy

[harleysportster]

If you are loosing spark on one cylinder once its hot, it's a bad CDI box, which is a very common problem with that model year.

[Sloan]

If you are loosing spark on one cylinder once its hot, it's a bad CDI box, which is a very common problem with that model year.

Actually - the guy I bought my first JD sled from (76 - 440) thought it was the CDI also. He eventually replaced the stator = since he could not return the CDI he gave it to me along with a part sled. If you want to try the CDI I still have it sitting on the shelf - just pay the postage. If it solves the problem then give me what you think it is worth. I still have the old stator if you want to get it rewound.

[Viktory2k1]

get the CDI box. Same thing happened to mine many years ago. If it fixes your problem give sloan an extra tip because these things aren't cheap anymore.