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DocBA
01-12-2012, 11:54 PM
I am a professional automotive technician and cannot get this thing running. It has fuel, I have fed it with carb cleaner, I have even fed a little gas in the combustion chamber. So fuel isn't the problem. I have a strong blue spark from the plug, the plug is new, and has been gapped to specification. I'm guessing it's a timing issue. The only way I get his thing to fire is if the muffler loads up with fuel and goes off. Timing check to come.....anything I might be missing/suggestions would be great.

Thanks,
Brad

muthey
01-13-2012, 03:27 AM
Air if you are not getting proper air flow it will just flood. Have you cleaned the air filter,re-oiled it and checked the airway through the frame for a plug? Also in the bowl base of the carb there is a starter jet down one of the holes. If that gets plugged it will wreak havoc on you. Yamaha is really simple for timing, if you have the manual, and check to make sure the marks line up at tdc then it's right. Here is a link to a downloadable manual http://www.oscarmayer.net/atc/manuals/

DocBA
01-17-2012, 10:14 PM
Air flow wasn't much of an issue as the filter isn't hooked up right now. Timing checked out spot on. So I brought home my compression gauge......30lbs. I adjusted the valves.......40lbs.....I added some oil to the hole and....45lbs. Now my abbreviated manual, doesn't mention it, and only having an iPhone for Internet I can't view the large manual, I believe that this is WAY under specification. So what are my common problems here? Need to re-ring it? Valves? Bore it and stick in a new slug? It's not the effort of rebuilding this that bothers me. It's the possible monetary outlay on a bike that was given to me, after someone welded a 400ex front end on it....bastards. Anyways a little help getting started in the right direction would be great.

DocBA
01-18-2012, 08:23 PM
Sorry about the rant last night I was more than a little upset. I'm guessing here that my next step would be to pull the head and check for leaking valves? Any guidance in this area would be great as small engines aren't my specialty.

swampthang
01-18-2012, 08:34 PM
Have you tried pull starting it with another vehicle? If you have fuel,spark and the timing is right then it should start if you get the motor spinning over fast enough even if it has low compression.

DocBA
01-18-2012, 09:01 PM
No, haven't tried pull starting it. Did put heavier oil in the combustion chamber, compression jumped to nearly 90lbs, confirming my worst fear. That this machine at minimum needs rings, I have never rebuilt one of these, so help gathering a parts list and/or suggestions for ringing this thing would be great. Right now I am assuming I need a base gasket, rings, a headgasket, valve seals, a new plug, and a carb kit. Any suggestions??

Thank,
Brad

swampthang
01-19-2012, 11:25 AM
Do a search on this site for the manual of your bike and download it. It pretty much will tell and show with pictures how to disasemble,repair and reasemble your machine.

DocBA
01-19-2012, 01:44 PM
I have the link to the manual, however only have an iPhone for Internet at the house. The IT guy at work says a manual that large kills the bandwidth and screws up the parts department's computers. Odds are the machine has been hot, and probably scored up the piston and/or the cylinder. Just trying to gain a little bit of insight and knowledge from the people who frequent this board. I'm sure there are many here with much more knowledge about these bikes than I have.

Brad