My '77 xs360 idles normally when i first get it started but has very little torque/power when I ride. After about 20 mins of riding something happens, usually sounds like a large backfire, and the bike starts running very well with a lot more torque. However, when this happens the bike idles at about 3500 rpm. Any ideas what's going on here? I am a complete n00b, this is my first bike.

  On 4/24/2010 at 7:00 PM, 1977XS360 said:

My '77 xs360 idles normally when i first get it started but has very little torque/power when I ride. After about 20 mins of riding something happens, usually sounds like a large backfire, and the bike starts running very well with a lot more torque. However, when this happens the bike idles at about 3500 rpm. Any ideas what's going on here? I am a complete n00b, this is my first bike.

could be only firing one one cylinder and the backfire is unburned fuel igniting and then working.

I suggest a tune up of ignition/timing

drewps

  On 4/24/2010 at 7:04 PM, drewpy said:

could be only firing one one cylinder and the backfire is unburned fuel igniting and then working.

I suggest a tune up of ignition/timing

drewps

Thanks for the response. When it first starts and rides poorly, there is still exhaust coming out of both pipes with equal strength. Would that happen if only one cylinder is firing?

  On 4/24/2010 at 7:14 PM, 1977XS360 said:

Thanks for the response. When it first starts and rides poorly, there is still exhaust coming out of both pipes with equal strength. Would that happen if only one cylinder is firing?

yes, but to check; feel the exhaust and they should both be the same (hot) temperature

how long of a warm-up do you try ? older 1s need a few minutes

  On 4/24/2010 at 7:19 PM, drewpy said:

yes, but to check; feel the exhaust and they should both be the same (hot) temperature

You were right, the air is cooler out of one pipe until the engine starts idling at 3500 rpm, ie. the other cylinder starts firing. Any idea what could explain the high rpm while idling? I left the bike running for about 20 minutes thinking it might eventually go down but it didn't

sounds like a big air leak!

is the rubber manifold capped off/secure?

spray th inlets with carb spray and see if the engine fires on that side

  On 4/26/2010 at 4:11 PM, drewpy said:

sounds like a big air leak!

is the rubber manifold capped off/secure?

spray th inlets with carb spray and see if the engine fires on that side

Looks like an air leak might be the problem...how do I spray the inlets? Does that involve removing the carburetor?

  On 4/26/2010 at 5:14 PM, 1977XS360 said:

Looks like an air leak might be the problem...how do I spray the inlets? Does that involve removing the carburetor?

no you start the engine and spray around the carb inlet and listen for it firing