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Message started by Tocsik on 06/10/14 at 12:05:38

Title: quick question on cleaning TEV
Post by Tocsik on 06/10/14 at 12:05:38

will there be free-flowing fuel in that part of the carb without the motor running?
I have the Raptor (as of last night) so I can switch it off and run the gas out of the carb, but do I need to do that?
Thanks.

Title: Re: quick question on cleaning TEV
Post by Dave on 06/10/14 at 12:08:17

Nope....it pulls fuel up from the float bowl. I believe it uses the Enrichement Circuit to obtain fuel.

Title: Re: quick question on cleaning TEV
Post by Tocsik on 06/10/14 at 12:58:39

Thanks Dave. I've only had the bike a week or so. It's an '08 with about 3K on it and it gives the really loud KAPOW when I shut it down and pops pretty loud when hitting the throttle and letting off while riding.
My first plan is to drill out the brass plug and back out the mixture screw a half turn or so.
I figure the TEV shouldn't be bad but since the bike has so few miles on it in 6 years there's a chance it could be gummed if a PO let it sit without proper prep.

Title: Re: quick question on cleaning TEV
Post by Dave on 06/10/14 at 13:27:35

The TEV has nothing to do with the shut down POW. When you turn off the ignition, the engine is still turning and it pulls fuel and air though the engine....and pumps it out the exhaust since the spark plug is inactive. When the fuel/air mixture in the hot exhaust is heated up to the flash point - it ignites. I lean mixture burns faster than a rich one....so if the bike is lean at idle the mixture is more explosive and makes a louder bang. Lawn mowers used to do this....and most modern mowers have a fuel shut off that closes when you turn the key off, and it prevents the bang caused by the hot muffler filling with fuel.

You cam limit the pops and bangs while riding, by holding the throttle open about 1/16 turn when you shift and decelerate. It makes very little difference in the amount of braking you have to do as it is not enough throttle to make any power....just enough to allow fuel to flow into the engine while you are braking or shifting. The pops and bangs when you shift or decelerate are caused by the engine going lean when you have shut the throttle and closed off most of the fuel flow...only the idle circuit is providing fuel. The TEV (Throttle Enrichement Valve) is supposed to add fuel when you have the throttle closed and the engine has gone lean....but it does not add much and doesn't seem to eliminate the problem. Richening up the pilot jet can reduce the popping and banging - but the problem is that when you make the pilot jet bigger to reduce pops and bangs - you may be running too rich and get crappy fuel mileage.

Dave

Title: Re: quick question on cleaning TEV
Post by shorty on 06/10/14 at 15:47:27

lean burns more slowly than rich, but the explanation still is accurate :P

Title: Re: quick question on cleaning TEV
Post by Dave on 06/10/14 at 17:24:03

7567687569686361060 wrote:

lean burns more slowly than rich, but the explanation still is accurate :P

Maybe inside the engine....but not in the muffler. The folks on this site who have had "gun shot" explosions on shutdown....then replaced the pilot jet with a larger one....or turned the mixture screw richer....report the explosion is reduced to a "poof".

Title: Re: quick question on cleaning TEV
Post by justin_o_guy2 on 06/11/14 at 04:40:56

Does putting a larger pilot in make ya a poofter?

Title: Re: quick question on cleaning TEV
Post by DavidOfMA on 06/11/14 at 07:05:38

4E75796973711A0 wrote:

I got ride of the downshift and decel pops on my bike by cutting one-half of a turn off of the TEV spring, after turning out the mixture screw didn't solve the problem. Keeps the TEV open slightly longer. YMMV.

Title: Re: quick question on cleaning TEV
Post by verslagen1 on 06/11/14 at 07:20:33

05030E0E0A03080F050413610 wrote:

Title: Re: quick question on cleaning TEV
Post by DavidOfMA on 06/11/14 at 09:14:54

273423223D3036343F60510 wrote:

[quote author=05030E0E0A03080F050413610 link=1402427138/0#7 date=1402495538]I got ride of the downshift and decel pops on my bike by cutting one-half of a turn off of the TEV spring, after turning out the mixture screw didn't solve the problem. Keeps the TEV open slightly longer. YMMV.

This is a trial and error fix, plan on error and you'll be ok.for some adding a washer did the trick.

I'd clean first, try some other adjustments next, maybe a thin washer, then get another spring to try long before modifying the hard to get stock spring.[/quote]
That's just what I did. I cleaned the TEV and carb, adjusted the mix screw, tried a larger pilot jet (got rid of the backfire but wouldn't idle when cold), tried a washer, and tried a softer spring. The softer spring got rid of the backfire but caused an irregular idle. I also read through the threads on the spring mod for the TEV and saw that most people were removing a substantial piece of the spring. I started with a half-round, and that tiny adjustment was enough to get rid of the backfiring. Of course, as I said, YMMV.