Back Fire

[dna9656]

A few weeks ago I rode the 83.5 VR to work; when I left work I turned the choke ON (because I have been buying High Test gas (92) ) and twisted the throttle a little and hit the starter. it cranked but no start. I repeated this a couple more times and then remembered that the book says to set the choke, DON'T give it any gas and hit the start button. So I did that and BOOM a huge noise. technically I don't think I had a back fire by definition; I think some gas got in to the exhaust and ignited; it was REALLY loud. Real back fires (IMHEXP) aren't that loud. So I left the gas alone and choked it a little and she starts...I travel about a 1/4 mile at 5 to 15 mph and then after a stop sign I started to accelerate and the bike bogs down like I created a huge vacuum leak, I back off the throttle a bit and the power comes back on, I drive another mile and try to accelerate again and it bogs down again, backing off the throttle returns the power. All the way home (26 freeway miles) I just do the limit (60 mph) or under. Getting off the freeway nearer my home I see if it will bog down again... NOW WAY...I try again and again and NO WAY will she bog down. At home I checked for popped off vacuum lines, the caps on the (BLOCK) YICS system are in place and I checked all the LARGE diaphragms on the carbs, all are intact. I drove to work today and NO PROBLEM...What cause the bike to loose power like that and then recover it self? Can I trust the bike to perform in a normal manner?

[GaryZ]

My guess is that you blew all the gas out of one or more float bowls. It takes a little time to refill and you were burning it faster than they could fill. You were repeatedly running out of gas!

[Marcarl]

I would guess that the 'back-fire' might have loosened a baffle plate in the collector, which then might have blocked the exhaust, causing your issue. Take a small hammer and tap the collector to see if you can make it rattle a bit.

[videoarizona]

My guess is you had some crud or water in gas??? Went through carbs and now gone...

[dna9656]

All;

I'm Pretty sure there was no water in the gas although it's certainly possible, I just went though a nightmare of water in the gas and that experience was nothing like this; as for blowing the gas out of the carb bowls that also occurred to me but then I don't think it would have run smoothly prior to the "cough", with one or more bowls empty it seems to me it would have run pretty rough. I think the fuel pump would have corrected the empty bowls fairly fast. It certainly would have filled the bowls after more than a mile of travel at 35 mph; during this more than a mile part it didn't miss or balk at all.

Now the baffle plate being loose, that makes more sense to me except it hasn't occurred again under any amount of throttle, bike lean, hard braking, quick starts, hot or cold engine temperature.

Certainly some kind of anomaly...

Thanks to all for the responses and ideas!

[Neil86]

Are the slides clean....wondering if some stuck open when it detonated and finally worked free?

[dna9656]

Are the slides clean....wondering if some stuck open when it detonated and finally worked free?

 

I checked the slides (are you referring to the cylindrical tubes that go across the throat of each carb. and diaphragm actuated and spring loaded correct?) and they are clean, I think you might be right that something broke loose and got sucked down and blown out....

[Marcarl]

Check your air filter, see if you burned a hole in it.