I just did the first compression test to my fj40 and i was wondering if my results show a strong motor or not. the numbers came out 160 150 155 140 140 150. I thought i had read on here before that 140 was what it came with stock, but i couldn't find that post. Does this show carbon buildup or anything? thanks
compression test
- Thread starter 72FJ40
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if i rember right i think that the stock compression for the 1f moter that you have is 149psi. you alson dont want more than a 20% differance between any two cylinders next to one an other.
good numbers
Your data indicates that you have good compression - I had only slightly better data from a fresh re-build.
I ran an engine for years that varied between 135 and 100. Yours likely has a long life ahead of it.
Your data indicates that you have good compression - I had only slightly better data from a fresh re-build.
I ran an engine for years that varied between 135 and 100. Yours likely has a long life ahead of it.
Those are great numbers. Don't waste them on an aftermarket carb. A motor that good really deserves an Aisan.
- Thread starter
- #7
i don't plan on swapping carbs, the stock one seems to be running fine, although the plugs were a little black. i adjusted the idle misture screw in a little, i hope this helps. thanks for the info, i'm very glad ive got a strong motor
72FJ40 said:
Good to hear you have the stock carb. Stock carbs rarely blacken plugs. I'd be looking for a weakened spark to explain the blackened plugs. Just a thought.
- Thread starter
- #9
hmmm i don't know, i have had the cruiser for a couple years and just replaced the plugs, maybe because they have been in for a while they are black? i thought black plugs were a sign of rich running, so i screwed the idle mixture adjuster in, maybe that was the wrong thing to do. I used to always run it with the choke pulled out a little (1/4"), maybe that caused the blackening?
the only way to adjust a idle mixture is to use a vacume gauge. having the RPM's at 600 you want to adjust it untill you reach max vacume.
Yes, running with the choke out richens the mixture and would tend to carbon up the plugs. Were the plugs black on the electrodes, or just around the rim?
Vacuum gauge runs about 20 bucks. Great investment.
Yes, carbon on the electrodes could mean cool plugs, but it generally means incomplete combustion, and a rich mixture. The carb may need to be rejetted, or it may mean a vacuum leak, or a number of other things. Vac Gauge is a good start.
Yes, carbon on the electrodes could mean cool plugs, but it generally means incomplete combustion, and a rich mixture. The carb may need to be rejetted, or it may mean a vacuum leak, or a number of other things. Vac Gauge is a good start.