Discussion:
Need help- '73 Clark C500 running like dog doo (long)

Here's the background story-

At my work we have a '73 Clark 6000 lb capacity forklift. I'm kinda the "do everything" guy here so forklift operation and maintenance both fall under my jurisdiction, so to speak. The forklift is powered by a gas Continental flathead straight six. We've had this forklift for a little over a year, and it really has not run correctly since we bought it.

Toward the end of last summer, I was running the forklift for an hour or two moving some stuff. The gas gauge on it isn't hooked up, so I didn't know what my fuel level was. It ran fine (well, as fine as it could, it's had some issues since we bought it) until I parked it.

A few days later I went to use it and it started, sputtered and died. Subsequent attempts to start it also failed. I opened the side cover and the fuel filter was full of rusty sediment from the tank, apparently the gas was low. (The forklift sat for awhile before we bought it so it had some crud in the tank. There is no provision to drain the tank on this thing so I haven't been able to do anything about it)

I changed out the fuel filter and added more gas- no go. We called out a service technician from a local forklift place and he said the fuel pump was dead, so I got a Carter P60504 inline electric fuel pump for it, and a holley 12804 regulator. Got all these installed, the pump works great and seems to move plenty of fuel, but still no start.

So, last week I pulled the carb off (Zenith 1 barrel updraft) and ordered a "repair" kit for it. To my dismay I found out the "repair" kit did not include any jets...only a needle & seat, gaskets, and a new idle screw. At any rate I tore the carb down...it had a little rusty sediment in the bowl but otherwise looked pretty good. I soaked it overnight in carb cleaner, blew out all the passages with carb cleaner, adjusted the floats, replaced the needle & seat, checked out all the jets, put it back together and put in the new idle screw.

I installed it a few days ago and attempted to fire up the forklift again. Well, now it would least idle (which it would not before) but it would still not run properly. The idle is low and adjusting the idle screw seems to have little to no impact on the idle speed, except that if you run the idle screw all the way in it'll shut off. The throttle is also very slow to respond. The exhaust smells like gas.

I should add that the spark plugs and wires are fairly new as I replaced them last year and we don't use the forklift too often. I have a new points and condenser but have not replaced them yet because the old ones looked pretty good.

Also- I installed a pressure gauge on the regulator. I currently have the regulator wide open because I found conflicting specs on the pump, but I don't know for sure yet. However I never get any sort of a pressure reading on the gauge. Any ideas there? Should I just take the regulator off? Supposedly the pump does 4-7 psi.

I tried to start it yesterday and while it would start, it was idling extremely low, just going "chug chug chug"...sounded like an old steam locomotive. This is similar to what it was doing before. If you tried to give it throttle it would start to rev up slowly, then choke out and die.

Thanks for any help- I really don't know what the deal is with this thing. I figured cleaning out the carb would fix it but it hasn't.
  • Posted 21 Feb 2009 03:06
  • Discussion started by garrett_h
  • West Virginia, United States
'73 Clark C500-HY80
Showing items 16 - 19 of 19 results.
You might want to check your valve clearances, these sometimes close up with valve seat wear an you loose your compression.
  • Posted 21 Feb 2009 04:23
  • Reply by AndyPandy
  • Staffordshire, WM, United Kingdom
I saw that discussion, but being that it was LP powered I wasn't sure how similar it would be.

I guess I should try doing the cap and rotors if I have them. But, this is seeming (to me) like a fuel issue. I did pull one of the plugs and it had a good spark. I have a spark tester at home but I keep forgetting to bring it in.
  • Posted 21 Feb 2009 03:54
  • Reply by garrett_h
  • West Virginia, United States
"chug chug chug" sure sounds like a blown head gasket, check compression
  • Posted 21 Feb 2009 03:42
  • Reply by mrfixit
  • New York, United States
Take a look at the discussions on 2/20/09 - that might give you some hints - I realize the Contiental F163 is a 4 cylinder & yours has a Contiental F227 6 cylinder.

Also remember this unit is 36 years old.
  • Posted 21 Feb 2009 03:27
  • Reply by johnr_j
  • Georgia, United States
"Have An Exceptional Day!"

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