Back firing when down shifting

[Mosborough Piper]

Just picked up (about a month ago) an 05 Midnight RSV and am LOVING IT!. My first bike was a Yamaha Roadstar Silverado. I bought it about 4 years ago and put on about 35000KM. Took a RSV out on a test ride at Americade last year and got the bug.

 

In the last two weeks or so it has started to back fire when down shifting and when starting cold the choke doesn't always "catch". I have to rev the throttle a little for the choke to catch. I am thinking I need to get the carbs synced but not sure. There is also a gasoline smell when I shut her down or go to start her up....

[Dano]

Possibly getting a stuck float and a good synch job. Try running some Seafoam thru there and see what happens.

 

Good luck

[Mosborough Piper]

Thanks Dano. I'll give both a try and see if it works

[V7Goose]

Do a search for older posts, you will find tons of information on this, including some fairly detailed explanations from me on exactly what is going on. Carb sync is the first and most important thing, as it can fix the problem and will improve everything about the way it runs. After that, the most likely cause is a vacuum leak caused by cracked rubber caps on the vacuum nipples or a nicked vacuum hose from someone pulling them off with pliers. If those caps are the original ones on your 05, they ARE leaking.

 

Many here will tell you to disconnect the AIS system to simply hide the problem instead of actually finding and fixing it. Personally, I think that is a VERY VERY BAD IDEA. Although disconnecting the AIS will have no negative impact on your bike at all, neither can it do anything to improve the way the bike runs. All disconnecting the AIS does is hide the problem you already have while it increases the polution. The fact is, these bikes when properly set up and completely stock will NOT pop and bang on decel, so there IS something wrong - the fresh air inducted into the header pipe through the AIS valve is simply giving you advance notice that you have something wrong before it gets bad enough to affect the way the engine runs. Good luck getting it sorted out.

Goose

Edited September 26, 2009 by V7Goose

[hunter 1500]

The LC1500 used to do that until I took the pair valve off. Is that the same with these bikes?

[V7Goose]

The LC1500 used to do that until I took the pair valve off. Is that the same with these bikes?

A PAIR valve is pulsed air injection - performs the same function as our AIS system. The difference is that our AIS is a completely passive system that just lets the vacuum in the exhaust header suck in some fresh air when the AIS valve is open. The function of both is simply to let the unburned hydrocarbons in the hot exhaust continue burning before they are blown out into our breathing air (kinda like having someone walk behind the horses in a parade to scoop up the road apples). The systems have a valve that closes from high engine vacuum when the throttle is snapped shut because the concentration of unburned hydrocarbons is just so high at that moment that they all cannot be burned without causing the explosion and loud bang.

 

So like I said above, if you are getting that afterfire explosion, it means something is causing the unburned fuel in your exhaust to be higher than normal, and it is so high at the beginning of the deceleration that you get the explosion before the AIS valve has had a chance to completely close. Best to fix that problem than just hide it and ignore that it exists.

Goose

[Mosborough Piper]

Awesome. Thanks Goose. Found the related info you spoke about. What a great forum this is!!!

[csogbk]

I have this same problem on my 09 RSV, I know the carbs are in sync because KiteSquid so graciously helped an old Army guy out and took care of them for me. Its not a bad backfiring, just occasional, and every now and then I get a whiff of gas as well.

[crockettrider]

D

 

Many here will tell you to disconnect the AIS system to simply hide the problem instead of actually finding and fixing it. Personally, I think that is a VERY VERY BAD IDEA. Although disconnecting the AIS will have no negative impact on your bike at all, neither can it do anything to improve the way the bike runs. All disconnecting the AIS does is hide the problem you already have while it increases the polution. The fact is, these bikes when properly set up and completely stock will NOT pop and bang on decel, so there IS something wrong - the fresh air inducted into the header pipe through the AIS valve is simply giving you advance notice that you have something wrong before it gets bad enough to affect the way the engine runs. Good luck getting it sorted out.

Goose

 

 

Isn't that a little bit like saying you shouldn't take Viagra cause while it might help it's only masking the hidden problem?

Not that I take Viagra:big-grin-emoticon:

[V7Goose]

Isn't that a little bit like saying you shouldn't take Viagra cause while it might help it's only masking the hidden problem?

Not that I take Viagra:big-grin-emoticon:

Only if Viagra stops you from farting.