gutted airbox?

[bigneily]

gonna try twin pipes on my 670x , was told to gut the airbox if i say don't like the pipes and choose to remove them and go back to the lightweight can and my old jetting specs, will the jetting most likely be off from the gutted airbox. or is modding the airbox better all around anyhow...

 

[MURDOCK]

Twins, gutted air box, up one needle, two mains, run a lower clicker#....you won't take them off.

 

[bigneily]

thanx

 

[bigneily]

Twins, gutted air box, up one needle, two mains, run a lower clicker#....you won't take them off.

on my 98 670x it still has the factory dpm setup if i jet up two sizes from what i'm running now will the dpm system compensate for any differences either lean or fat, or could i haveto maybe go 2 1/2 sizes over for example....

 

[NoSecondChances]

on my 98 670x it still has the factory dpm setup if i jet up two sizes from what i'm running now will the dpm system compensate for any differences either lean or fat, or could i haveto maybe go 2 1/2 sizes over for example....

DPM only compensates for alt and temp changes, nothing else. So if you jet lean (14:1 air/fuel ratio), it will run lean at 1000 ft and 10000 ft. If you jet fat (11:1 air/fuel ratio), it will run fat at 1000 ft and it will run fat at 10000 ft. Its based on the DPM and all other alt compensators only compensate for altitude and temp changes, your baseline jetting still determines the overall air/fuel ratio in your motor, the DPM just maintains that ratio as you go up or down in elevation or the temp changes. The compensator just changes the amount of fuel that goes in based on temp or alt changes. Go up two sizes but if you are running stock jetting on the 670 right now without the twins, you will likely end up back where you started but better to start fat and work back to lean. Go up two sizes and run around, check the plugs and see what they look like, then drop back down a size or two until the plugs and wash look good and it is crisp and clean.

You can't go 2.5 sizes up, it will either be a little fat at 3 sizes or a shade lean at 2 sizes (as an example). If 2.5 is what you need, then you are better to go to 3 IMO and keep thing safe.

I'm with Murdock, I'd gut the airbox with the twins and run it like that. Depends on who's twins you are running and where they make power you might want to crank your RAVE valves out a little bit, you'll lose a little low end but they will run better on the top possibly. Who's twins? Is it those Gagne ones?

NSC

 

[bigneily]

yup it's the gagne's got em in my shed takin up space still debating on putting em on.some guys tell me twins are nothing but a pain in the arse , especially spring riding when the temp warms up, constantly playing with em. thought of trying them the other day but it was -20 when we left the parking lot, i didn't want to be playing with jetting when it is that fresh out..

 

[Zachmandu]

I run SLP's on my old 670, with a 501 RV and a ported case. I LOVE it. I run from sea-level to 3400', and have had NO tuning issues at all. Spring time, winter time, high temps, low temps, boondocking, hillclimbing, trails... I was REALLY surprised at how consistant it runs. I beat on it for three seasons with nary a problem. Now the ol' sled is "retired"...

I looked into gutting the airbox, and searched around, but from what I read, gutting the box makes the sled MUCH more finicky to jetting depending on temps and elevation. In addition, I think that I read that the BSFC goes WAY up, and the sled starts burning ALOT more fuel. For the gains made vs. the trade-offs, it just didn't seem like the right choice for me. If you gut the box, and don't like it, I have a couple stock airboxes lying around I would part with.

I had a 670x, wanted twins for it, but could never find a set that met my price range - CHEAP!!

 

[NoSecondChances]

yup it's the gagne's got em in my shed takin up space still debating on putting em on.some guys tell me twins are nothing but a pain in the arse , especially spring riding when the temp warms up, constantly playing with em. thought of trying them the other day but it was -20 when we left the parking lot, i didn't want to be playing with jetting when it is that fresh out..

Yep too chilly to be playing with cold fuel and fingertips.....

Those Gagnes were race pipes, you will want to back the RAVE's out a ways. You will lose some bottom end with them probably but you should notice some good pick up on the top end. I run Jaws pipes and I love them! Have run them from 2500 to 9500 ft and no probs, same thing as Zach, hot, cold whatever, they work good. Sometimes it would be nice to have a single but 80% of the time I want the twins so it works well.

 

[bigneily]

what does backing the raves out accomplish? and how much should they be turned out? or is it something like turn it out and try it idea?...thanx..

 

[NoSecondChances]

what does backing the raves out accomplish? and how much should they be turned out? or is it something like turn it out and try it idea?...thanx..

Twins are not known historically for making gobs of low end power. Backing out the RAVE's spring cup (little red thing on the RAVE cover) allows the slides in the RAVE that slip into the cylinders to open the exhaust port sooner and get into the powerband of the pipes (slide moves out farther as the exhaust pressure increases) and lets the twin pipes really breathe in the upper RPM where they make the most power. Its a "turn it and try it" sort of thing, you might find they make good power cranked all the way in too. I would try it cranked all the way out too though, as you might prefer the high end power to the lower range or vice versa. Something to play with and a simple adjustment can make a noticeable difference.