coil

Checked the spark on my 98 YZ 250 and the spark is yellow, not blue. So i checked all the ignition components as the manual stated. The only thing i found that was out of spec. was the primary coil resistance reading. The manual says it should be 0.20-0.30 ohms, i got a reading of 0.70. So can anyone till me for sure if the coil is really bad with this reading. It appears to be from the reading. but I'd still like opinions before I spend the money.

bikepilot said:

The higher number means it has more resistance than it should, beyond that I am not much help. How does the bike run? I had a CR500 that was a nightmare to start and did not run very well at low rpm...lotsa backfireing etc...The coil tested slightly bad...dont remember the specifics, but I ended up getting a new one and the difference was night and day. I weighed 125lbs at the time and suddenly had no trouble starting the CR500:)

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Thanks for the reply, The bike is really hard to start. Once i get it going it will run good if I don't shut it of . After shut down it won't start or starts and fouls a plug. I've been trying everthing to get the bike to run right. At first i thought it was jetting, which it may be. I went from a 172 main to a 168, 48 pilot to a 42 , and one step leaner needle and it still fouls the plug. i replaced the transmission side crank seal think that was the problem , still fouls plug and har d to start. i'm sending the cylinder to Eric for porting and top end evalaution. I'm thinking maybe the top end is shot and thats causing the problem or this coil is the problem. Thats the history so far. Any opinions are appreciated.

Ol'89r said:

oldgoat.

If the rings are bad and the compression is low, it will make the bike hard to start. As far as the coil goes, I would recommend trying to find another coil to borrow and switch with your coil just for checking purposes. Sometimes they will check bad with the tester and be good and visa versa.

You may want to do a compression test.

Just my $ .02

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Thanks, I have the top end apart and I checked the ring gap, spec's call for 0.55-0.75, I have 0.70. The limit is 1.3, this is all in mm

i tryed to check the Compression but my compression guage won't clear the top frame rail, have to find a new one I guess.
i always hated the mid range hit so i decided to let Eric Port it and check the top end for me. i figure let the experts do there thing since I don't know how. maybe he'll cure my problem.