Road Star Forum	ForumThreaded ViewRules

Welcome, Guest Please Login or Register.    Lost Password?

Favoured: 0

TOPIC: Re:Quick HSR42 - AFR Question Forum Tools Post New Topic Show latest posts Rules

#299197 Ruprect (User) BLACK RHUBARB FOREVER ! Junior Boarder Posts: 197 Quick HSR42 - AFR Question 1 Year, 10 Months ago   I am running an HSR42 with a ported manifold & huge K&N. I did a dyno run recently after everything was set up and got some really good results (mostly interested in AFR #'s but also got 73hp and 99 lb-ft). Full throttle AFR is about 12.8 from 2700 rpm to 3500, then it leans out to about 13.2 until redline. Cruising AFR is great (about 13.2 - 13.8 across the board on 25% and 50% throttle). My question is: I'm running a 165 main now (AFR 13.2 @4500 rpm). What can I expect to see as far and AFR change if I go up to a 167.5 ? I'd like to see it @ 12.8 across the board on full throttle if possible. Thanks, Rup   Logged     We\'re gonna need a bigger boat . . . . .   The administrator has disabled public write access. #299204 DocShadow (Admin) Hmmmm .... send beer Admin Posts: 17615 Re:Quick HSR42 - AFR Question 1 Year, 10 Months ago   I don't think you're going to get what you want. At WOT the needle is out of the jet so the AFR reflects the jet size. If you increase the jet size then the AFR at + 3500 rpm will decrease as you wish but then it will also decrease at 2700 - 3500 rpm. Doc   Logged     My Bike Website   The administrator has disabled public write access. #299211 Curt (Moderator) Never to old to ride! Moderator Posts: 12504 Re:Quick HSR42 - AFR Question 1 Year, 10 Months ago   Not sure if you are running one but a Yost Power Tube might get you the results you want without changing your jet. Just depends on if you want to spend the money and experiment a little with it. I was getting those numbers with a 40 CV carb but I am at 483 above sea level. I haven't dynoed mine with the 42 yet as I am going to put a 45 on it.   Logged     My Site Black Ice is Shiny, Black Ice is Deadly, Ya Wanna Ride My BlackIce?   The administrator has disabled public write access. #299281 Erbman02 (User) Platinum Boarder Posts: 3800 Re:Quick HSR42 - AFR Question 1 Year, 10 Months ago   I hope you were doing this run in 4th gear, and at 2700rpm you wouldn't be at wot. For wot in 4th, you would be up around the rev limit. I've been using the same dyno for the past 5yrs, for wot, he always does this in 4th and rpm just 100rpm shy of limiter. I've been using this article for their chart for AFR   Logged       The administrator has disabled public write access. #299298 Ruprect (User) BLACK RHUBARB FOREVER ! Junior Boarder Posts: 197 Re:Quick HSR42 - AFR Question 1 Year, 10 Months ago   The run was 4th gear, throttle snapped wide open starting @ 2500 rpm or so and holding wide open until red line. I realise that wide open throttle on a flat slide at low rpm is not ideal, but thats how it's done apparently. The 50% throttle numbers are probably more realistic for low and mid rpm's. My real question is: how big of a difference in AFR above 4000 rpm can I expect with a main jet increase from 165 to 167.5 ? I'm just worried that jetting up will make too big of jump and I'll be overly-rich at high rpm. Thanks,   Logged     We\'re gonna need a bigger boat . . . . .   The administrator has disabled public write access. #299304 Erbman02 (User) Platinum Boarder Posts: 3800 Re:Quick HSR42 - AFR Question 1 Year, 10 Months ago   I see at 4500rpm you are at 13.2, my preference is to be between 12.5 to 12.8 to aid in keeping head temps down and to prevent detonation in 5th gear roll-on, not 5th gear hammer it. I seldom have to lower a to 4th if already at 75, 80mph to pass   Logged       The administrator has disabled public write access. #299430 Ruprect (User) BLACK RHUBARB FOREVER ! Junior Boarder Posts: 197 Re:Quick HSR42 - AFR Question 1 Year, 10 Months ago   I realise that I may have to drop the needle to compensate for a bigger main jet in order to keep the mid-rpm AFR #'s where I want them. But my question still remains: how much of a change can I expect to see in afr above 4000 rpm going from a 165 to a 167.5 ? Thanks,   Logged     We\'re gonna need a bigger boat . . . . .   The administrator has disabled public write access. #299485 Curt (Moderator) Never to old to ride! Moderator Posts: 12504 Re:Quick HSR42 - AFR Question 1 Year, 9 Months ago   Not a lot 2.5 jump isn't much you can fine tune with the needle. The Yost power Tube kit I got the main increase in jumps of 5.   Logged     My Site Black Ice is Shiny, Black Ice is Deadly, Ya Wanna Ride My BlackIce?   The administrator has disabled public write access.

Forum List Technical Corner Jetting

...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... -->