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Hey my 1983 Yamaha maxim xs400 backfires a lot and won't quite turn over. It will run for a little but at about 500 RPMs and then eventually die. I can do this repetedly until the battery dies. I just can't seem to get it above 1000 RPMs.

Any ideas?

Clean the carbs then add an inline fuel filter?

What do the plugs look like? Are they fouled? Do they smell like gas? Are you getting consistent spark with them? Carbs clean and free of debris? Gas not too old?

That should give you a start.

I had the carbs cleaned and syncronized at a shop about a month ago. At the time they replaced an in line fuel filter. They also replaced the spark plugs at that time.


It was at that time that put some gas in the tank so maybe its already old. At the time it doesn't seem like I am getting consistent spark. At time I will pull the plugs just to check the spark and on one side there will be no spark. The next day I will look at it again and it will be fine. When I pull the plugs they are black and moist with gas.

The last time I had the carbs off was to clean the little passage in the float bowls. The ones that control gas at idle. I wasn't getting my left side to fire consistently so I thought I would clean them out. One side was definately plugged and the other had crud in it. I cleaned them both out really well checked the other passages to make sure they were still clean (they were) and put the carbs back together.

I got the bike in October from a gentleman who had let it sit for 9 years. It hasn't run regularly since I have gotten.

Thanks for the ideas.

Peter

This same problem started with my 82 Seca. No one could tell me what was wrong. Tried everything -- carbs cleaned, plugs were fine, all of it. It just never recovered. I was happy to get rid of it.

canuckerjay wrote:This same problem started with my 82 Seca. No one could tell me what was wrong. Tried everything -- carbs cleaned, plugs were fine, all of it. It just never recovered. I was happy to get rid of it.

not great news but the earlier I find out the better. I suspect its electrical but I don't know enough about wiring to deal with it and since I got the bike for free I don't want to put a ton of money into it.

WHen you say that the plugs are black... Is that oil on it? Cause you may get oil in the combustion chamber which is sing of avdanced wear of your engine.