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A chainsaw that I have been working on keeps fouling plugs on cold starts. The manual calls for an RCJ7Y Champion spark plug. I went to a parts store and they sold me a CJ8 Champion spark plug. I gapped them to .025 like the manual said and they still fouled on cold starts. The chainsaw is a Poulan Wild Thing 2375-1. What would be a hotter plug to use? What spark plug gap should I use?

I would think you have another problem other than the plug but the hottest plug in that size is the NGK BPMR4A

I think star is right. Please define "fouling plug on cold starts" do you mean the plugs gets wet with fuel mix and then misfires? Spark plug heat range doesn't come into play till the engine is up to operating temp.

Here is a good pic of plug details. Explains heat range.

I agree, you have an excess fuel issue fouling plugs. Too much oil mixed in, fuel mix not shook up or filthy carb. Cracked fuel lines....



slomo

You could try one of these. I use one in a 10 year old Echo trimmer and stopped having to take a break after starting it. I don't use it much anymore so I can't tell ya how long it will last, but I do know swapping it in during a tune-up produced a marked improvement where it runs better than it ever did new. You might want to gap with a feeler gauge instead of one of those keychain sliders. The iridium electrodes tend to stick on the slide gauges and produce false measurements.

Well this thread is from 20 days ago.
JMB never bothered to come back but I think I saw the same thread on 2 other forums.
If you actually read the post and not just jumped in to spruke your fix for everything you would have noticed that the plug he was supplied was a plain CJ8 which while being the next grade hotter is not a direct replacement for an RCJ7 as it is not a resistor type plug so will fire too early which is probably why the engine would not start .

Either that or more likely he was having carburetor problems. But when the OP don't close out a thread we never know if he got it fixed, still working on it, gave up, or found the unit un-repairable.

I working through a Stihl FS106 repair right now that would have been not repairable if wasn't for the customer having a donor engine as the PNC is no longer available. Now just getting the gaskets is the next thing now.

The darn thing ran even with a badly scored PNC that was loose. It should have never ran.

jmb2641f7k said:

A chainsaw that I have been working on keeps fouling plugs on cold starts. The manual calls for an RCJ7Y Champion spark plug. I went to a parts store and they sold me a CJ8 Champion spark plug. I gapped them to .025 like the manual said and they still fouled on cold starts. The chainsaw is a Poulan Wild Thing 2375-1. What would be a hotter plug to use? What spark plug gap should I use?

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Fix the fueling issue and run the standard OEM plug. Unless you run the saw at full beans, a hotter plug is a waste of time. Plug won't heat up enough to burn off. Saws are meant to run WOT.

slomo