Sinc. carbs but have problem

[Vonwolf]

Hi;

I haven't seen this problem before so here goes.

I got a cheap 87 VR 1300, the bike runs OK but rough ran Seafome thru it changed plugs. It helped a Little but still very rough Idle and back firing some manly on deceleration.

I decided to sync. the carbs. Problem is the bike runs so rough the vacuum gages bounce so fast you cant see then, they just vibrate in a range of about 1/3 the gage blindingly fast?

I have a sinking feeling its the valves are out of adjustment some thing fierce but thats just a guess.

I'm hoping some one here is familiar with this condition and can give me a hand, any thoughts will be greatly appreciated.

Thanks Pete

[wes0778]

Go by a store that sells aquarium supplies and pick up a couple of air tubing cut off valves. Put them in line with your vacuum gauge(s) and open it just enough to show a steady vacuum reading.

[skydoc_17]

Hey Vonwolf,

Use the Idle Adjustment Screw to raise the RPM'S above 2000 and see if the Vacuum levels out.I take it you are not using a Carbtune Manometer? If you have a Carbtune, there are 4 restrictor tubes that will take care of the problem. Another Idea is to have a friend hold the throttle at 3500 RPM'S and set the Carbs, once set try them at idle and it should be easier to read.

Earl

[Vonwolf]

I have 3 of the cut off valves but didn't know what they were for, makes sense now, I'll try to get a 4th valve and hope for the best.

Thanks for the great advise

[Harmonicashawn]

If Vacuum is not steady, that indicates problems with valves not seating properly. Worst case scenario is a complete valve job, but an adjustment may be all that is needed.

[MiCarl]

If Vacuum is not steady, that indicates problems with valves not seating properly. Worst case scenario is a complete valve job, but an adjustment may be all that is needed.

 

There is a difference between unsteady vacuum and the normal rapid pulsing that occurs in the intake. You need a restriction (near the vacuum port) and a significant volume (long hose) between the restricter and the gauge to damp the oscillations.