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521 has no power :(


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Hey Guys


Well I've been driving my new 70 521 around and it is sucked out! It makes a bunch of noise but over about 2100 RPM it just seems to run rich and not go any faster. I have trouble getting it over 40MPH and if theres any slight incline it wont even make it to 40.


I've done a tune up, set timing to ~10BTDC and hasnt made any difference. Vacuum is about 16" at idle. I'm beginning to wonder about carb and/or timing chain loose. Are there any common causes of what I'm experiencing?


Also I'm not sure if its related or not but the truck will not fire with the choke on. I have to leave it off to get it to fire then pull it out a bit to keep it running when cold. Do these truck carbs have a cold high idle? I didnt see anything.


My feeling is the truck is getting too much fuel and flooding since I can see the black haze behind me when I put my foot down.


Help please I'd like to enjoy this truck to putt around in but right now its almost undriveable :(

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521 has no power


Yes, that's true. But it should run better than that.



Your vacuum is low.

the truck will not fire with the choke on

Check the float level. You can just look through the glass site on the carbureotr.It should be very close to the line.


It's unlikely to be a 'loose chain', but a compression test will tell you if the chain is OK or not.

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Thanks guys


I noticed the fuel line is about half an inch above the line on the float bowl. So I'll start there. Does anyone know a good place to find a rebuild kit for these hitachi carbs?

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Put some rags under the front of the carb and remove the sight glass and holder. NOTE the float is on a hinge pin. On the outer end just behind the glass is a small brass spacer. Very small and will fall off and get lost. The float, if lifted very very gently until the inlet needle is closed, should be level. Yours is likely too high on the pass side which will allow the fuel level to be too high.


Clean the glass and the 'rubber' seal carefully and you should have no problems with leaks. Check after starting for any wetness and again after a few days.

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Figured out the problems


1st off my glass sight on the carb was upside down so the line was near the bottom not the top.


2nd the secondary wasnt opening with vacuum.


Fixed those issues and its running way better! Its like its a supercharged from 30 hp to about 70 lol

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