I just bought a mint condition 1981 CB900 custom. The seller was very up front that the bike has been sitting for a couple of years. The brakes were a mess but I have fixed them. Now for the fun part! I drained the tank and put fresh gas in it. I tool off one of the carb caps and it looked ok. I figured what the hell and tried to start it but nothing. The battery has been charged but dies after a few minutes of trying to start. Before I go ripping this thing apart can anyone get me started in the right direction of what I should do????

 

Rebuild the carbs and put new plugs in it... you may have to flush the gas tank too, rather than drain and fill or else the carbs will just get gummed up again.

 

Thanks! That is what I thought but was hoping not to have to do.

This may be a foolish question but what would I use to flush the tank???

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wchandler &raquo;</TD></TR><TR><TD CLASS="quote">
This may be a foolish question but what would I use to flush the tank???</TD></TR></TABLE>

If there's rust in it? Phosphoric acid. If no rust? Some water/simple green to clean the varnish out.

 

use a bunch of ball bearings, throw them in with some degreaser and shake the crap out of the tank. make sure to count the amount you put in, so none of the little guys end up in a fuel line

I use this trick for lots of things....cleaning coolant overflow resevoirs, etc.

I had a bike once, that ran, but only on one cylinder(v twin). Just ran some seafoam through it and after a couple days, all the varnish cleaned out and it ran like new.. This isn't a typical scenario though.

 

So I pulled the carbs off and started to rebuild. It didn't look too bad. I think bad sparkplugs, totally rotted air filter and a mouse nest built in the air box was the main problem...

I didn't touch the pilot screws or floats. Is there an easy way to check the floats without a float gauge. Also, I don't want to mess with the factory setting of the pilots. My manual says to count the number of turns until it seats on the seal and use that for a gauge. How sensitive are these if I don't get them back exactly how they were???

Thanks!

 

If the floats look ok, just make sure you put them back in the same carb they came out of. For the pilot/air screw adjustments, the bike will be sensitive to turning them - 1/2 turn off either direction is a big change.

Good luck

 

Ok, I am almost there. Thanks for the replies. I have another question which is: How do I check for spark? With my old push lawnmower I used to put the plug in the spark plug cap and crank the engine a few pulls and you could see if the plug was lighting up. Anything similar to that? I would imagine it would be more technical. I am just trying to cover all possibilities before putting the bike back together.

Thanks!

 

Nope, thats what I do - Make sure you ground the spark plug threads against the engine case, rather than just holding the electrode up to the engine case - if the plug is fouled, it will not spark if you ground it with the threads.

Get the carbs rebuilt?