Well I've been working on the bikes carburation, nothing new for a Firestorm owner that likes to tinker but, after wearing out 3 sets of VTR carbs over the years, I have learnt something that I must share with you Guy's.

I know there are many varied carb set-up combinations that seem to work for many, mine is even more away from others due to the 2 into 1 and opened-up airbox. There has been plenty of discussion over the VTR years of 3, 2 or 1 slide lift holes, also the use of Dynojet slide springs.

When I got this, my second Firestorm, I fired into it, changed the pipe, hacked into the airbox, set the carburation how I thought it should be, fantastic, loved it! Then with the talk of 1 slide lift hole being the go, and even HRC venturing down that path, I figured I better give it a go , which I did, the bike didn't go as good as it did before (both carbs are running short stacks), me thinking I need to play with the carb settings again, nope the bike had lost power and had a slight stumble at high rpm during fast gear changes that I could not jet-out, I chased my tail for a while, thought maybe I'd have to live with it?

Next change I thought I'd try; Dynojet slide springs (short), my high rpm fast gear shifts had an even bigger hesitation! So I learned, the issue with slide holes, is not how fast the slide lifts but how slow it DROPS. Snapping the throttle back on after a quick shift, the bike had a stumble because the slide was still high and the sudden opening of the butterfly gave the engine a gulp of air (lean stumble), I'd tried fixing it with pilot & needle settings ....... WRONG! Maybe the single slide lift hole might work for a stock airbox, the slight restriction might help pull some fuel out when the throttle is snapped open? I guess this why the Dynojet kit states that you need three slide holes when the short springs are used.

So I go back to a previous setting, the slide with the single hole I had drilled the hole from 2.5mm to 2.75 and araldited the other hole, so I drill out the Alaldite, so now I am at 2 holes, 1 x 2.75 and 1 x 2.5mm. Went back to my original slide springs, stockers with 50mm cut off and stretched back out to the 300mm length. Awesome! No stumble, full power.

If you are finding a stumble at high rpm with a sudden off then back on throttle, my guess is the slide can't keep up, if you are using 1 slide hole and/or short springs.

John Orchard

 

Guess this answers my question on the other post! You should keep these in one thread IMO.

 

Thanks, I keep them separate because they relate to different issues that VTR1000F owners complain, or show a misunderstanding, of, rather than confusing with too much info. If it was all a complete guide to how a carb works, then I agree it would be better together.

There are plenty of pages on the internet explaining how CV carbs work.

 

Hey, what ever you wanna do is fine by me.
Appreciate you stopping in to share your experience. We'd love to see some pics of your VTR, if you have any to share.

 

I just thought I'd give an update on what I am currently running ........

2 x short bellmouths.
2 x short Dynojet springs.
2 x 2.75mm holes in each slide.
Pipercross airfilter.
Airbox intake area doubled, no snorkel.
195 main jet front & rear.
42 pilot jets.
Float level raised 1.5mm in front carb.
Stock needles sanded down to similar to Dynojet specs.
Stock pistons & cams.
2 into 1 exhaust, original header pipes, 2" tail pipe with 2" straight thu muffler 570mm long.

And it runs FANTASTIC !!!!!