1972 Yamaha DS7 Issues

[Oldschoolbike]

Hey guys, new to the forum here 


I just inhered a 1972 Yamaha DS7.
Soaked the carbs and blew them out about 8 times now.
New floats and needles (even though the carbs sometimes overflow). Float levels have been adjusted perfectly.
New electronic ignition (Timing is set perfectly).
Mixture screws set to factory specs.
Idle was set using directions in manual.

The bike sounds like it idles slightly rough and left cylinder is either backfiring or skipping. Stops backfiring and skipping when running just that cylinder alone though. When I connect both plugs, it starts spitting again. Not sure if that's normal.


When I take the bike out for a spin it has absolutely no power even in lower gears. Forget about making it up any hills. The island I live on has lots of short steep hills everywhere.
After running for about 5-10 minutes left cylinder will stop firing.
I'm thinking the coil could be bad?
Maybe there's something plugged up in the carbs that I can't see?
The bike has been sitting since 1975 so that carbs were pretty gunked up. Only ran a few times prior to being put away.
Any help would be appreciated. This bike is driving me up the wall.

[dgorms]

Living on an island I would check every electrical connection! Unscrew the plug leads and clip a quarter of an inch off the coil wires. Check compression. Revisit carbs! Been sitting for 50 years needs crank seals.   

[m in sc]

check charging voltage and if the coils/wires are original, change them. also, is the airbox/filter stock? if not, it needs to be rejetted.

[dgorms]

Bear in mind they don't make any real "power" til 4 or 5k rpm.

[Oldschoolbike]

Okay next question is it 100% needed to change the crank seals if the bike has been sitting so long. Also the bike smokes a ton when I really give it throttle when I get into its power band. Is this normal or could that be the crank seals going bad on me?
I had the bike running really nice for about 2 hours and then one of the wires for the ignition shorted out on me. Prior to this 2 hour run, I took small copper wire and pushed it through the little holes in the carb. Best it's ever run. So maybe those little holes were slightly plugged up.

[dgorms]

It's cheap insurance against melting it down!

[m in sc]

best to take the carbs completely apart and clean them. yes change the crank seals