Crank seals or CDI box

[liquidatorkid]

worked on my 76 JD liquifire with a 440 koritz in it today, hooked everything up, cleaned the carbs, new coils, new gas lines, new fuel pump, went to run it and it would only run on one cylinder, it would cut in and out beetween both cylinders, i did how ever check to see if the spark was cutting in and out, i pulled the PTO side plug wire off and no change still would run on one cylinder, tried it again but pulled the recoil side plug off and it died right out so obviously it wasn't running on the PTO side cylinder, i did change the plugs with a new pair and still the same thing it would only run on one cylinder, i did take it for a quick spin and it would cut in and out of running on both cylinders,both cylinders seem to have good compression, and good spark when the plugs are outta the cylinders, so i am thinking it has to be an issue with maybe the cdi box, or the the center seal in the crank???? any ideas or suggestions? i was thinking about running a leakdown test on it to see if the center seal may be shot

[harleysportster]

If you still have the original Prestolite CDI box, I would say that is bad. When they fail, it is common for the spark to drop out on one side, then the other. One thing to remember, never pull a wire off of a spark plug while the engine is running. This overloads the CDI box and shorts it out internally.

[liquidatorkid]

i believe it is the original cdi box, and when i did the cylinder drop test i had it shut off then i pulled the plug wire off and it made no difference with the PTO side plug wire off, then i shut it off, and plugged the plug wire back on then unplugged the recoil side plug wire and nothing, so that's telling me that there is a spark/cdi issue with the PTO side cylinder i Harvey a spare plug cdi box i am gonna try tomarrow and see if i can get that to work, let me tell you when both cylinder kicked it it flew haha i was surprised lol

[liquidatorkid]

i swapped out the CDI boxes today, squirted some oil/gas mix in the carbs and it fired right up and ran on both cylinders for about 15-20 seconds, and now it isn't getting fuel up to the carbs it is getting fuel to the lines where the lines are attached to the fuel pump, Ive checked the fallowing, the vaccum line from the crank to the fuel pump. that's is working, took the fuel pump apart looked clean and not damaged, put new lines with hose clamps on the vaccum line from the cases to the fuel pump, from the fuel pump to both carbs, i pulled the gas line off from the front of the tank its getting fuel there, and also i took the line off that connects from the tank to the fuel pump at the fuel pump, and its getting fuel, i just don't get it, its getting fuel out the fuel pump to the lines that run up to the carbs but its going up the lines about 1/2 way up the carbs then is going right back down to the fuel pump and not making it to the carbs, sounds line an air leak in the lines? I'm sure everything is tight with the hose claps i replaced

any idea's or suggestions what it could be?

[Matt]

You mentioned the center crank seal earlier, but have the outer seals been changed?

[lwb140]

has your pickup fallen off in the tank !! shine a light in the tank and see maybe the check valve stuck in the tank

[liquidatorkid]

couple more weeks till the triathlon, had to go through and replace the cdi box, fuel pump, all lines and clamps, cleaned the tank, took the fitting outta the tank and the whole pick up line was rotted right off, and there was no check valve in the tank, so i got that all fixed up, and still runs on one cylinder then both so i am gonna replace the crank seals in it this week and prolly give it a fresh new top end, other then the crank seals, re jetting the carbs to the 440 specs, putting a different hood on it (hinge cracked completely outta the hood) i wanna make a pair of scags for it or find a set of carbines for it for the races

here is the info i got off from my liquifire the chassis is a 76, the motor is a KEC-440/23LC # is 746201781 and the carbs are off a 76 340 i believe they are the original carbs that where on the original 340 koritz i took outta the chassis, correct me if I'm wrong the 76-78 liqufirue 440's all used the KEC 440/23LC, just wanna make sure i order the right parts, also what is the std. pore piston and rig size for the kec 440/23LC 66mm?

[harleysportster]

[quote="liquidatorkidhere is the info i got off from my liquifire the chassis is a 76, the motor is a KEC-440/23LC # is 746201781 and the carbs are off a 76 340 i believe they are the original carbs that where on the original 340 koritz i took outta the chassis, correct me if I'm wrong the 76-78 liqufirue 440's all used the KEC 440/23LC, just wanna make sure i order the right parts, also what is the std. pore piston and rig size for the kec 440/23LC 66mm?
][/quote]

Shannon,
The kec 440/23LC was the model of the engine used in all the 76 thru 78 Liquifires, but there were changes thru the years. One thing to note thou is the 76 engine is jetted differently than the 77/78 due to a higher compression ratio and the use of high octane gas. The gasket kit and pistons will interchange but technically the original base gasket is different between the 76 engine and the 77/78. The compression ratio was lowered as well.
If the original coolant tank is still on the engine, the 76 had a metal baffle under the cap, this was deleted in 77.
The standard bore is 66mm. You need to take the engine apart and measure the pistons and cylinders to determine what is worn. At the least, just installing new rings will improve the engine along with a light hone.

[liquidatorkid]

went to the local dealership today and ordered the full gasket kit with crank seals $42.99, and both ring sets for the pistons $8.99/set, they will be in wends, then ill have to get the correct VM34-125 carbs, i called up the local salvage yard and he said it would be $60 a set if he has a pair of them

[Matt]

Maybe I missed something, but i don't think you need carbs, you just need the correct jets for them.

[harleysportster]

All the jets and slide valves is different from what he has. It may be cheaper to find the 77 carbs.

[liquidatorkid]

got the motor outta the chassis all torn apart, got the flywheel off and had to take it to the local dealership to have the clutch pulled off so today i split the cases and inspected the crank, everything besides the PTO side crank seal looks good, all rod bearing and crank bearings look good, no horizontal or vertical plat in the lower rod bearing, no heat marks and everything rolls smooth and freely, i did notice the PTO side
crank seal was oval shape and was sloppy on the crankshaft, would make sense why it would only run on the recoil side cylinder, the full gasket kit, crank seals and new std. rings will be in wends, and while I'm there I'm gonna have them hone the cylinder's out $10 a cylinder not too bad, and i also found a good clean set of vm34-125 carbs for the 440 koritz, have to change out the main jet to a 220, the jet needle to a 6DH4-4, and 1 float pin and they will be ready to put on and tune in, so by this weekend id like to get everything put backed together and take it for a spin, also cleaned up the cases and other parts in the parts washer

[JDT]

Interesting carbs you got there.

What are they from again?

[liquidatorkid]

the carbs are VM34 125 i was told this is what the 440 liquifires used, the only things i had to change in them was the need, and the pain jet, the pilots and other jets where the same, i am just waiting on the needles to come it, i got the motor completely put back together with new gaskets, new rings, and got it in the chassis yesterday got everything all hooked up , runs good just needs some fine tuning on the carbs idles too low, and the belt seems to be worn down alot so this weekend i am planning on taking it down to my friends garage and tune it up and get it ready for the triathlon

[thevintagesnowmobile]

My 76 liquifire is doing the exact same thing as yours. I replaced the pto side crank seal and I thought it was fixed but it didn't last long. After riding it for a while one cylinder shuts down and it won't run on both cylinders again until it's cooled down. Please let us know what you find out with yours.