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Ch740 spitting fire

#1

J

Jbeavis19

I'm having quite a bit of trouble figuring out what is worth with this engine. Carb has sat with water and fuel in it and when running the exhaust glows and has a flame coming out of it.

Things I've done so far:
Magneto driven ignition update + plugs
Inspected bottom end timing components
Inspected flywheel key
Replaced lifters that appeared to have stuck baskets
Carburetor cleaning

Nothing has made any improvement in running rich and burning fuel in the exhaust.

I didn't check after the new lifters but before the swap the base circle of the cams seemed to have pressure on the valves. Does this engine use different length push rods for intake and exhaust? Maybe they got swapped at some point.

I'm torn between getting a cylinder leak down tester, just getting a valve job done, and swapping the carb.

Any thoughts would be appreciated.

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#2

Scrubcadet10

Scrubcadet10

The only time i've seen exhausts glow like that is when the engine is running too Lean. what do the spark plug electrodes look like? are they a tan-ish white or black?


#3

I

ILENGINE

Lets start with the full model number including spec number from the engine tag. Also what was the part number of the ignition update kit that you used. Wouldn't be the first time I have seen the spark advance ignition system being used on an engine that had fixed timing initially or vise versa.


#4

J

Jbeavis19

The only time i've seen exhausts glow like that is when the engine is running too Lean. what do the spark plug electrodes look like? are they a tan-ish white or black?
They are brand new and gapped before installation.


#5

J

Jbeavis19

Lets start with the full model number including spec number from the engine tag. Also what was the part number of the ignition update kit that you used. Wouldn't be the first time I have seen the spark advance ignition system being used on an engine that had fixed timing initially or vise ve


#6

J

Jbeavis19

The engine is CH740-0045. At least that's what the manufacturer's website says. The sticker is completely worn off the engine.

I used:
25-584-15-S coils
25-351-11-S lifters


#7

J

Jbeavis19

They are brand new and gapped before installation.
I used Champion platinum 3071 gapped to .030

Now that I'm double checking the plugs, I may have gotten them wrong though. Still not likely to be my biggest problem.


#8

I

ILENGINE

It appears that is the incorrect module for your spec number. Your engine calls for the 25 584 14-S, 24 584 15-s would of been correct for pre MDI conversion as an older part number prior to the 24 584 36-s module. But the 25 584 15-s is used on a different engine than yours. Could be causing spark timing issues. lifter part number is correct for your engine.


#9

M

MParr



#10

J

Jbeavis19

It appears that is the incorrect module for your spec number. Your engine calls for the 25 584 14-S, 24 584 15-s would of been correct for pre MDI conversion as an older part number prior to the 24 584 36-s module. But the 25 584 15-s is used on a different engine than yours. Could be causing spark timing issues. lifter part number is correct for your engine.
Thanks, I'll try the others and let you know how it goes.


#11

I

ILENGINE

Thanks, I'll try the others and let you know how it goes.
Make sure you pay close attention to the part number starting with 24 and the part numbers starting with 25 in my post. that difference could be confusing.


#12

J

Jbeavis19

Good read, unfortunately they're selling without a resolution.


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