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General Discussion / Re: Any old boys still here ?
« Last post by holeshot buddy on June 21, 2024, 08:16:32 pm »Just checked in been a long time loved this forum so much information would be nice to see it back how it was 
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General Discussion / new member wushing to join
« Last post by PeterC on June 21, 2024, 08:18:26 am »Andy, from Minnesota USA, (this has come from my facebook feed), has tried to create a login but was unsuccessful. I firmly believe forums offer decent advice etc compared with Facebook etc and try to always direct users to Forums.
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Tech Talk / Re: 1980 RM 400 fouling plugs
« Last post by Wasp on June 15, 2024, 03:00:29 pm »What sort of plugs are you using ? That could be a good starting point to look at.
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Tech Talk / Re: 1980 RM 400 fouling plugs
« Last post by PeterC on June 14, 2024, 08:43:22 am »Please let us know how you progress. Grest ride
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Tech Talk / Re: 1980 RM 400 fouling plugs
« Last post by John Orchard on June 13, 2024, 11:08:15 pm »If it appears to be blowing way too much smoke (oil), maybe it has a damaged crankshaft gearbox oil seal?
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Tech Talk / Re: 1980 RM 400 fouling plugs
« Last post by maxi81 on June 13, 2024, 08:13:49 pm »Thanks for the replies. Conondale was really the first time I have had a good ride on it since restoring it. The bike was originally my Dad's who bought it new. I'm also running a new Mikuni VM36 carb which doesn't like the standard jetting from the manual. Will play around with the jetting and go from there.
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Tech Talk / Re: 1980 RM 400 fouling plugs
« Last post by PeterC on June 13, 2024, 09:25:54 am »There is a wealth of knowledge on here. Beware of blanket statements like " run 40:1 Motul". We do need to know much more background on the bike. Sounds like a great bike. Hope you enjoyed Connondale!
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Tech Talk / Re: 1980 RM 400 fouling plugs
« Last post by skypig on June 13, 2024, 08:52:49 am »My question would be:Has this bike previously been running well, and not fouling plugs? (Or is it, the bike, new, to you?)
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Tech Talk / Re: 1980 RM 400 fouling plugs
« Last post by pokey on June 12, 2024, 07:21:52 pm »Every doofus has an opinion on oils and most would be wise to keep it to them selves. As the lads have said your premix ratio isnt the problem. Oil is used to lubricate and cool an engine and many air cooled engines run at 20:1. The more oil molecules in a mix the less fuel molecules for the same amount of wet stuff so the engine will run leaner.
Conondale isnt at that high an altitude at 150M to make a lot of difference. Jetting is the answer after of course you make sure the float level is set and the air cleaner and the pipe are clean and clear to allow the engine to breathe. If it cant breathe it's like running with the choke on.
Conondale isnt at that high an altitude at 150M to make a lot of difference. Jetting is the answer after of course you make sure the float level is set and the air cleaner and the pipe are clean and clear to allow the engine to breathe. If it cant breathe it's like running with the choke on.
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Tech Talk / Re: 1980 RM 400 fouling plugs
« Last post by pmc57 on June 12, 2024, 11:56:21 am »I'll preface this by saying I'm no expert but have read up on two-stroke tuning and follow the rationale, also owned a few early RM's over the years. This may help you to understand mixture settings in two strokes.
Many believe that by running less oil in their premix it helps to stop fouling by creating a so called "leaner" mix. In fact it does the opposite. By decreasing the amount of oil in your premix, you're allowing more fuel molecules into the "fuel (oil)/air mix" that's being created by the carby. Think about it, by decreasing the amount of oil, the void created is taken up by more fuel. As most of us know, the more fuel in the air/fuel mix creates a RICHER fuel mix, while less fuel creates a LEANER fuel mix. In your case you've created a richer fuel/air mix simply by removing some of the oil thus more chance of plug fouling happening.
If you want to run 40:1 or 32:1 (less oil than manufacturers recommendation) then you will need to re-jet to a smaller main jet (top rev range) and probably lower needle position (mid rev range) so a 'light tan" is achieved in a high rev plug-chop test. If you're running standard jetting now, then go back to the manufacturers recommended premix ratio which I'm sure is 20:1 for those bikes and see how it goes, you may be surprised.
Hope this helps,
Cheers
Many believe that by running less oil in their premix it helps to stop fouling by creating a so called "leaner" mix. In fact it does the opposite. By decreasing the amount of oil in your premix, you're allowing more fuel molecules into the "fuel (oil)/air mix" that's being created by the carby. Think about it, by decreasing the amount of oil, the void created is taken up by more fuel. As most of us know, the more fuel in the air/fuel mix creates a RICHER fuel mix, while less fuel creates a LEANER fuel mix. In your case you've created a richer fuel/air mix simply by removing some of the oil thus more chance of plug fouling happening.
If you want to run 40:1 or 32:1 (less oil than manufacturers recommendation) then you will need to re-jet to a smaller main jet (top rev range) and probably lower needle position (mid rev range) so a 'light tan" is achieved in a high rev plug-chop test. If you're running standard jetting now, then go back to the manufacturers recommended premix ratio which I'm sure is 20:1 for those bikes and see how it goes, you may be surprised.
Hope this helps,
Cheers