where should i start with jetting after motor build
07-28-2011 | 06:04 AM
#1
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From: south nj (philly area)
where should i start with jetting after motor build
I have installed je 11.5:1 .05 oversized pistons mori stg 1 cams mori +1 mm valves and ported head where should I start with my jets?? I have the factory pro ti jet kit...
07-28-2011 | 09:32 AM
#3
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From: Atlanta, GA
I would go back to a stock filter and start with stock jetting, or try the jetting you had before the mods and go from there. I can't remember what I ended up with, but I think it's at least one jet size leaner than it was before the high compression pistons because the engine is now more efficient.
Anyway, in my case the jetting wasn't too different than before.
Anyway, in my case the jetting wasn't too different than before.
07-28-2011 | 12:49 PM
#4
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From: south nj (philly area)
Why go back to the stock filter? I got the k&n because my stocker is no good and I want to be able to wash the filter instead of change it didn't do it for power plus I got it cheaper than a stocker from Honda...
07-28-2011 | 01:02 PM
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I agree. Some say it's impossible to make a SHawk run right with the K&N, but after a few hours of tinkering with mine, it runs just fine with the K&N. Go up one jet size from stock on pilots and mains, and start from there. You have done some serious mods to the engine, and no one will be able to tell you what you need now. It's all going to be trial and error till you find the right combination. Jetting a bike is not rocket science to get it close, but getting it perfect is an art.
07-28-2011 | 01:37 PM
#7
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And for what I would start with would be (again with a stock filter) is #48 pilots with 178f\180r and go from there. That is if you are using the stock velocity stacks in the stock configuration along with my standard carb set up (which you can find by doing a search) 
07-28-2011 | 02:02 PM
#8
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I have one but have never even bothered to try to get it jetted right. I did put it in one time but it was so far from right that I just took it out and put it in a box.
The consensus among those with lots of experience tuning Superhawks is that the K&N gives no gains and is more trouble than it's worth to get right.
07-28-2011 | 02:14 PM
#9
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The K&N increases airflow over the stock filter... And since the VTR has no lack of airflow unless you get really serious with the engine mods, it's not really an improvement... Plus, it tends to increase airflow unevenly across the revrange, which is why most of us find it to be a PITA to tune with... Yeah, you can make it work, but it's always, always a compromise... The only way you get a good setup with the K&N is by sacrificing either midrange by having it lean there, or top and bottom by being insanely rich there... Can't both have the pie and eat it...
BTW, the engine mods you stated isn't "getting serious"... It's just getting started, you will still have plenty of airflow with a stock filter... Changing the stacks gives better gains...
BTW, the engine mods you stated isn't "getting serious"... It's just getting started, you will still have plenty of airflow with a stock filter... Changing the stacks gives better gains...
07-28-2011 | 03:50 PM
#10
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With the K&N air filter, D&D's, and aftermarket Jetting, my bike had a lot of lag. It just felt funky, almost like it was trying to die. Got the K&N cleaning supplies, completely flushed it, put it back in looking like it was brand new, and maybe got a 3% improvement. Went on here, they told me to get rid of the K&N, so I went to BMC. INSTANT fix. No lag, no nothing. Even did the swap back just to make sure I didn't do anything else. The K&N ran just fine with Stock jetting, at least from what I remember. But if you do anything to the engine, as tweety once put it, K&N + Lighter Fluid + Match = Problem Solved.
When it comes to modded Superhawks, K&N= GARBAGE
When it comes to modded Superhawks, K&N= GARBAGE
07-29-2011 | 01:20 PM
#12
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08-09-2011 | 03:10 PM
#13
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Ive been on the bmc website to try and do some research as to the difference between the race and street versions of their filters...
from what I understand the filter size for both is the same 168mmX187mm however the filter media for the race version is more free flowing...
the website also states that you can tell the difference between the 2 by way of a yellow/orange stripe over the filter media...
a few years back I purchased the race version or so I thought from a distributor but I dont have that stripe... maybe Ill give them a call about it
Anyways... why is it that you dont want the race version? I would figure that the velocity stacks are what mostly determine air volume/velocity entering the engine and not how much clean air is entering the air box at any given time/speed...etc
from what I understand the filter size for both is the same 168mmX187mm however the filter media for the race version is more free flowing...
the website also states that you can tell the difference between the 2 by way of a yellow/orange stripe over the filter media...
a few years back I purchased the race version or so I thought from a distributor but I dont have that stripe... maybe Ill give them a call about it
Anyways... why is it that you dont want the race version? I would figure that the velocity stacks are what mostly determine air volume/velocity entering the engine and not how much clean air is entering the air box at any given time/speed...etc
08-09-2011 | 03:41 PM
#14
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The race version has the same issues as the K&N. The real issue isn't just that they flow more air. The problems comes from the pressure fluctuations and turbulence that they cause inside the airbox.
What this does is cause strange signals to the air bleeds (which determine the flow through the main jets and a couple other circuits) and gives you rich and lean spots in the power band. Also a flow commander will only kind of help out as there are 3 air bleeds to deal with.....
Sure some folks have said they have got them to work but in my experience, I could never get the results I wanted.
The only way to really get then to work right,IMHO, is to plug the air bleeds and run smaller main jets. Though this causes another set of problems to deal with. That is why it is (or was) generally only used on the stage 2 race bikes with ram air. As they were onlt really looking for top end power it worked good in that application.
Now for a bike that is going to spend most, if not all, of its life on the street, you want a big fat, broad torque curve. In my tuning experience on the SH, the most reliable way to get that power curve is with a stock filter. This is true up to and including a Stage 1 engine.
This is why I always recommend running the stock air filter.
Last edited by 8541Hawk; 08-10-2011 at 10:57 AM.
08-10-2011 | 10:57 AM
#16
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08-10-2011 | 03:00 PM
#17
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From: boston
well its a good thing your here... you have satisfied much of my desire for new knowledge and I need all the information I can get in prep for my stage 1 build so it all goes smoothly (maybe I can make a couple bucks off the bmc to help pay for stage 1)
as always thanks you
as always thanks you
04-13-2012 | 03:07 PM
#18
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From: south nj (philly area)
ok after reading and looking at my carbs i found that they have a dj kit in them... i got a stock filter and now my questions are im obviously gonna need stock slide springs but what about the needles can i use the factory pro ti needles i bought or are they not gonna be right? if those needles will work do i still plug one stock lift hole (obviously i already plugged the dj hole)... or do i leave it and use the factory pro pilots? if they wont work (or will be a pita to get only semi right) obviously i follow the set up sticky... and with the porting and bigger valves i would think it would flow more air thus needing bigger jets to compensate or am i wrong in thinking this??
04-18-2012 | 12:59 AM
#19
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The last Stg 1 engine I jetted I used the set up from my carb thread with the exception of the mains.
On those I went up one size which was to install the 178 from the rear carb in the front carb and ran a 180 in the rear and had excellent results.
On those I went up one size which was to install the 178 from the rear carb in the front carb and ran a 180 in the rear and had excellent results.
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