Although not a Vision a similar bike question

[nvdranger]

while out of town this past weekend, I got to take out a 1980 Yamaha 880 ("special" i think it said on the badges). ?not as wide as the vision and didn't seem to cut the corners as well. ?we were at the g/f's cousin's place in Yankton, SD and the guy has to many toys, the guy owns 8 bars/restaurants/businesses so he doesn't get to use them all and knew I was tyin get mine going. ?He only rides a couple time a year, but was in great shape and very very very clean. ?Anyways its another rare bike from what I was told with a 3 cylinder motor. ?Not as quick of the line as the Vision but probably a higher top speed than my 82. ?Man did it sound good, had the louder harley rumble to it. ?
Enough rambling and cut to the chase, when i would slow down by letting the motor do the work/meaning no brakes and sometimes down shifting or just letting off the throttle it work backfire several times (2-5 times). ?with my limited knowledge I assumed dirty carbs, but the were just dipped and boiled (neverheard of doing that) with new jets and what not. ?He a rich guy and pays to have everything done, in other words had no idea what I was talking about. ?I meant to ask about a carb synch and was thinking that may be the issue.
Question #2 - tach prblems. at idle it would seem right about 1200 give or take. ?start to take of and it wouldn't go above 3k and the motor sounded at about 5-8k depending. ?wiring maybe/where would we look to fix this?

Thanks in advance
Ken

[Walt_M.]

Popping off throttle can be caused by too tight valve clearance. Should check that then re-synch the carbs. And the bike is an 850.

[admin]

the old xs850 triple, cool bike. I almost bought one in 1980
but about a week later the seca 750 came out and I was sold.

as far as the backfire goes, my guess is an air leak in the exhaust, especially where you mentioned that it was a bit loud.  number 2 would be to look at the carb sync settings etc.
weird on the second one, so your saying that the tach is off by a few thou?  this may fall back to the first issue in that it might have a tci or ignition problem of some sort.  you'd have to run some tests on that one.

-Ron

[nvdranger]

the thing with the tach really stumped me. ?at idle it seemed fine but no matter how quick or slow i got on the throttle it barely moved at all. ?at about 65 it was reading 2k but sounded around 4 maybe 5k. ?its weird and i'll have to bring the monometer the next time i'm up there to check the synch. ?now that i think about it the tips of the mufflers were rusted out. ?but please explain why that creates a problem b/c i'm ??? ?is it similar to a car not having enough back pressure?

thanks
Ken

[admin]

slipping clutch maybe ?
bad ignition coil or ignition wiring, you'll want to go over all the wires thoroughly.
are you sure the clutch is not slipping ?

on the other thing,
fuel + oxygen + heat = combustion
if you have an exhaust leak that is pulling air in when you decelerate, you'll have a backfire problem.

also, quite possibly when the carbs were worked on, if the fuel mixture is too rich, you could have similar symptoms.

[nvdranger]

how would it feel or react if the clutch slipping? ?*EDIT* so the clutch is staying somewhat engadged so only some power is going to the rear wheel
thanks for the info, i'm gonna past this on to him and have him try to find the exhaust first and also have all connections cleaned/greased. ?Then see what happens and go from there.

Thanks again
Ken