Weak accelleration and performance when in gear

[buickyouth]

Recently, I replaced the spark plugs, fuel and vacuum lines, cleaned off the carbs, replaced the air filter and did an oil change with filter replacement.

Starting the bike up is much faster and easier now. And it seems to be a lot smoother at idle and when revving a little in neutral. Still, once any gear is engaged, accelleration is really really slow to respond and stuttering.

My first inclination is that it's a timing / carb sync issue. But I'm not sure.

Thoughts on troubleshooting and direction is greatly appreciated.

Thanks,
Ian

[3Phase]

Ian, sounds like the engine isn't hitting on all four. These engines will start and run on three, even two cylinders with just a little vibration, but they'll be down on power. You can narrow the problem by checking to see which, if any, header pipes are running cold or cooler than the others.

The headers get hot fast so be careful and don't burn your fingers! Just drip some water on the headers one at a time and if it sizzles, it's hot.

[CaptonZap]

Uuh, Scott, I think he only has three to start with, since I think that is what an XS750 is.
He might be better served on the triples board, <http://yamaha-triples.org/category-view.asp>,
although the physics is the same for all of them, so the trouble shooting will be the same. CZ

[petejw]

hi ian,

whats the history of the bike, did it have this
problem prior to u doing the work,
float levels can have a big affect on acceleration
have u set them correctly?
carb sync will always help as well,
u havent got any brakes sticking?
valve adj correct?
just a cpl of things to think about.

[3Phase]

Oops, I didn't see which forum this was in and there's no .sig info.

Still, troubleshooting is troubleshooting: Ian, check the exhaust headers to see if the engine is hitting on all three cylinders and if any of them are running cold then get rid of it and get an XS1100!

[Shacknasty]

If you haven't done a synch, adjust idle A/F mix, and synch again, that is where I would start.

Nuthin' wrong with a 750 triple. I like most of the XS series!

[rpgoerlich]

Might check/replace the plug wires and caps. If I remember correctly, the 78XS750 had an inline resistor in the plug wire.
Easily corrected with new wires, plug caps and resistor plugs.