81 LF issue.

[gracer]

My 81 Liquifire is hard to start after being warmed up.

A quick history. The sled was not running when I purchased it. So I went through it front top to bottom. The carbs are clean. Fresh hone and pistons and gaskets. New 108 clutch. New fuel pump ect…

Here is my issue.. The sled will start and run when cold. Just flip the choke and it will fire and warm up as expected and you can ride it. However once warm and you shut it off.. It is very hard to start. It will only start without any choke and zero throttle. Then it will putt putt sputter and die. Keep pulling (and pulling) and it will usually sputter to life and idle about 300 rpm. Touch the throttle it will die. Repeat this process and it may sputter up by feathering the throttle and run. By now I too tired to ride it. Let it sit over night or about 3-5 hours and it will run.

This sled has the major liquifire bog. Once up and on the pipe it scoots along.

My carb cutaways are 3.0. All the jets is in the carburetor are new. Running Stock
The electrical system is stock Stator, CDI, Coil. I have not changed the timing.

Looking to improve my Liquifire experience. This is the second year of with this sled with this condition.

Thanks

Greg

[lwb140]

got similar issues with a sled how much compression does it have ?? wade

[pjr]

My 81 Liquifire is hard to start after being warmed up.

A quick history. The sled was not running when I purchased it. So I went through it front top to bottom. The carbs are clean. Fresh hone and pistons and gaskets. New 108 clutch. New fuel pump ect…

Here is my issue.. The sled will start and run when cold. Just flip the choke and it will fire and warm up as expected and you can ride it. However once warm and you shut it off.. It is very hard to start. It will only start without any choke and zero throttle. Then it will putt putt sputter and die. Keep pulling (and pulling) and it will usually sputter to life and idle about 300 rpm. Touch the throttle it will die. Repeat this process and it may sputter up by feathering the throttle and run. By now I too tired to ride it. Let it sit over night or about 3-5 hours and it will run.

This sled has the major liquifire bog. Once up and on the pipe it scoots along.

My carb cutaways are 3.0. All the jets is in the carburetor are new. Running Stock
The electrical system is stock Stator, CDI, Coil. I have not changed the timing.

Looking to improve my Liquifire experience. This is the second year of with this sled with this condition.

Thanks

Greg

Greg,
Sounds like you've got the engine built and sealed up correctly, including the carbs, so here is what I *strongly* suggest that you do to this machine to make it REALLY run hard! I've had two 80's L/F's in my day and each of them were total performance turds when set-up to factory specs, where I couldn't stand to ride them because of the sluggish performance that I thought was unacceptable coming from John Deer's flagship sled of that day.

Like you, I was VERY disappointed with the performance and if you've read any of my past threads/posts on this board over the last 1 1/2 years, you'll find that I'm all about performance and efficiency no matter what I'm working on, as it's just my way as part of my profession/career. Follow my instructions here based on what I've personally done to BOTH sleds I've had and you'll have a new machine, where your "riding experience" this year will now be much better...


1. Cylinder Heads:
Ditch the low performance, low compression stockers that come on the John Deere Fireburst Kawasaki's and install a set of late 70's - early 80's Kawaski Invader heads instead. The bump in compression not only bolsters low-end torque, but it makes the engine purr along much nicer at all engine speeds. Plus it's **FARRRRRR** more responsive to throttle input than you ever thought it could be.

2. Ignition Timing:
Increase the intial ignition timing by approx. 3*-4* by turning the Stator back in the opposite direction of normal engine rotation, by placing the little timing mark tip on the Stator housing to the left (or top if you will..) of the timing mark on the case by 2mm. This will ***REALLY*** wake up the engine, make it easier to start and make it massively more throttle responsive also. Plus, you can still use 93 octane pump fuel.

3. Track:
The John Deere specs for track tension adjustment is just ***WAYYYYYYY*** to damn tight for that heavy duty, thick, Yokohama rubber track these L/F's use, where if you adjust it to the factory specs, it puts a ***LOTTTTTTTT*** of unnessary drag and additional load on the engine that eats up a TON of power! First, set the tension to factory JD specs, making sure it tracks straight on the bogies by running the sled in the air so the track can spin freely. Then loosen the tension adjustment bolts 2 full turns from that point and lock them down. You'll not only notice the sled will coast much easier when you let off the throttle, but you'll not have that artificial "braking" effect like you had before when the track was dragging, due to the tight JD specs. Do this upgrade and you will have free'd up a lot of power, the track will run cooler, the Hyfax's and drive belt will wear longer and the clutch won't have to work as hard to get the sled moving from a dead stop.

4. Secondary Clutch:
Ditch that junk, stock 44* single-slope L/F helix and install a 38*/44* dual-slope helix from a Sportfire instead. Then set the spring tension to the tightest hole (#4 if I recall correctly) and then preload the secondary spring 1 full turn after that before you bolt the helix down to the hub. This upgrade will let the engine rev out further before the shift to put the engine in it's peak powerband sooner AND it will backshift much quicker also when you're in heavy snow or under a lot of throttle load. The sled will be MUCH more spirited and you won't believe it's the same machine...

5. Gearing:
Last, but certainly not least and if you don't listen to anything else I've already said above, ***LISTEN*** to this!!!!!! GET RID OF THAT STOCK JUNK, JUNK, JUNK, HIGH RATIO TOP SPEED GEARING IN THAT THING.....PERIOD!!!!!!!!!!!!!!!!!!! The 80's L/F's were mostly equipped with 1.55:1 final drive gearing, making the sled a ***TOTAL TURD*** off the line, because the engine had to really lug hard to get "on the pipe", hence the common L/F bog everyone (including me) complains about. Install a final drive gear set from a 1980+ John Deere Trailfire 340 sled instead, as they were equipped with a 2.16:1 ratio to deal with the low power output of the baby 340 Fireburst fanner Kawi engine. This upgrade will make the biggest improvement of the performance of the sled over anything else I've said and your L/F will ***NOT***, I repeat, ***NOT*** have the dreaded "bog" any longer... It will climb on the pipe right away, scream to redline easily and launch that thing like you never thought it could!!


Trust me on this Greg, as I've done it now twice myself and all of these modifications/upgrades ***REALLY*** work very well without negative compromises. Parts are cheap, easy to find and you won't believe the new-found performance of this sled when you're done. Plus, the durability of the sled won't be negatively affected either... The performance improvement of the total package comes from the sum of the selected upgrades/modifications working in tandem with each other, so don't skimp out and do only one mod and not the other, thinking that it will be "good enough", because it won't and you'll be disappointed...

This is the way the factory should have done it and In my opinion, JD missed the performance target big-time by setting it up to perform "lazy" the way they did. The 1980+ L/F could have been a legend in performance for it's day with just a few tweaks that could have made that sled a real screamer!!

Good luck with your project and I said before coming from my own personal hand in doing this ....THIS WOKS!!!!!!


PJ

[gracer]

Thanks for the reply. My compression is about 120 even after a hone and new pistons. Bumping it up would not hurt any.

The fly wheel is being stubborn. Even with an air hammer on the puller is would not budge.

The gearing is going to be change to what was in a TrailFire. That should help.

As for the secondary clutch I would like to dump to and put on something a little more modern. The 7/8 in shaft is holding me back. I tried a brass bushing but the key ended up to be sloppy.

The sled is going under the knife for rebuild round #2.

Thanks again.

Greg

[pjr]

I looked through my parts collection I've amassed and I do have a 2.16:1 final drive set (top & bottom sprocket w/ matching chain) and a 38*/44* secondary helix here also for $50 if you need them.

PJ

[Sprailfire340]

Peeg -
If Greg doesn't take them I will...hopefully match up nicely with a new clutch I bought

[bruham]

Well for my 80 LF the only thing and first thing I replaced was the primary spring to a blue polaris spring and never had a bog everything else is stock...when I punch the throttle the ski's come up and so does 80mph....

[pjr]

Peeg -
If Greg doesn't take them I will...hopefully match up nicely with a new clutch I bought

He hasn't shown any interest in this stuff, so they are yours if you want them. Just give me a call or drop me a PM and I'll mail the parts off to you.

I'll even help you set your combination up over the phone too if it helps.

Peeeg

[ICCSF 108]

Ck to make sure your flywheel doesn't have a Electric Start Ring Gear on it, IF it does you Will Not be able to pull the flywheel unless you first remove the housing that the recoil bolts to ( the part that the CDI box also bolt to ) Parts book calls it a "cover" M68110 or M69232

Kenny

[427cobra]

I think it is your CDI. My buddy had the SAME issues last year. A CDI swap did the trick.

His would start fine when cold. But once warmed up you better not shut it off! You would have to let it cool down to start it....plus it was REALLY boggy!

So try the CDI swap then follow pj's tips to really dial it in!

[gracer]

Thanks -- I going to try the CDI exchage as the first test. I have a collection of motors the one can be pulled from.

Do the CDI boxes get warm and change the timing curve?

Greg

[JDT]

A bad or out of spec CDI can do all kinds of weird and hard to troubleshoot things.

No spark on one or both sides when it gets warmed up.
Intermittant spark on one or both.
Timing shifting way off(backfires and boggy.
Can idle ok but dies with the slightest throttle appliction.
And the list goes on.

When in dought try a different unit as it can be swapped out in a minute.
But don't forget to check the coils with a meter when they are cool and also when they are warm.
An ignition coil can be with in spec in the shop and be way out when it gets warmed up.

[Danzig...]

the cylinders were honed?

[JDCornFlakes]

Gracer....change the CDI yet ? Did it help hot starting problem ?
Or is it still an unknown ?

[gracer]

The new CDI is not installed just yet. I found a place that had a new aftermarket CDI box so I picked that up. Looking to get it in this weekend.

An new Coil is included in the purchase as well.

The plan is to do a number of things.

Install New CDI and Coil
Change the timing
Up the compression
Drop the gearing

My current motor the compression is about 118-120 on each side. This is with new pistons. A second set of heads from a spare liquifire motor have been sent off to get milled. Hope the cut heads come in about 135.

I can post an update on how this all goes. The goal is to have it up and running the weekend of the Jan 23.