1986 yamaha maxim 700

T

Trent

New member
Hey guys, ive been rebuilding this yamaha maxim 700 1986, its my first bike I've worked on, intensely. I have rebuilt the majority of it but im stuck on this starting problem. I've read other places with the same general problem, but no luck.
My problem is that it wont start no matter what unless it has sat under the hot sun for hours or spray starting fluid down the carbs.
Ive fully rebuilt the carbs inside and out replaced the spark plug wire and gaped the plugs, the spark plugs are a bit old, but no real ware and tare or damage.
Ive done eerything I can think of and just looking for some outside help.
Thank you guys
Trent





I know its a yamaha and kinda ****** year but its my first personal bike and wanted to rebuild something after my ex left
 
Not getting enough fuel, jets clogged? Is fuel getting to all the float bowls?

Petcock working properly/flowing enough?
 
You have obviously missed something. If it runs when feeding it eyther then fuel is the issue, Do carbs again or take to someone to have a second look. BTW eyther is VERY hard on your engine expecially if you just rebuilt it. Use propane its easier and safer. Simply feed raw propane into airbox using a propane solder torch, not lit of course. When it does start does it seem to run ok? Also wondering about timing both ign and valve.
 
I did put pod air filters on it

But as soon as its started it runs great keeps a low idle runs with power
it just keeps cranking and tring to start
I did a test to see if te gas is going through everything, it is
 
Have you checked the compression? Perhaps its not creating enough vacuum to vaporize the air/fuel while it's cranking. Also possible... a slightly clogged idler circuit. There are all sorts of little passages in carburetors that easily get clogged. Try getting the carbs done in an ultrasonic cleaner if you have access to one.
 
Seems like fuel is not going into the carbs, have tried checking the fuel filter and pump? Also double check the vacuum lines.
 
I'm familiar with that generation of Yamaha engines. There are a couple of things right off the bat that you need to square away.

1) Are the valves in spec? The good news is that valves are very easy on this bike.
2) How's the fuel/air mixture? If the fuel / air screws haven't been touched on the carbs, chances are very high that they need to be adjusted. These carbs are notorious for needing frequent adjustment. I mean twice a year adjustment. A Colourtune is the tool of choice here.
3) Are the carbs balanced / synced? Part of regular care / feeding of these carbs - they are very sensitive and are part of the twice a year adjustment.
4) Pod filters look cool, but the bike runs best with the stock airbox and the stock exhaust. The exhaust is less of a big deal, but pods make the carbs run more poorly at anything other than WOT.
5) Just because the spark plugs look ok doesn't mean they are. I'd strongly recommend replacing them if you don't know how old they are. In fact, bad plugs that look fine contributed to a problem on my 82 Yamaha Seca 750 (which is more or less the same motor) that resulted starting problems. New plugs are cheap - just replace them.
 
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