Jetting with Full Exhaust???
 

I have searched but haven't found a lot on jetting for a full exhaust system or maybe my search skills suck.

This is what me and a friend set it to a few years ago with me planning to get back in to it to fine tune. Never did and just rode it.


Here is my current setup:

Full Two Brothers Exhaust and that is it with Factory Pro jet kit.
Was running ok with the setup but not 100% and was a little rich. It would pop on deceleration but didn't have any noticeable bad spots.

Here is how my carbs are currently set:

Air screws 2 1/4 turns out front and rear
Jets 180 Front / 182 Rear
Pilots .48 Front and rear
Needles 4th Notch from Top front and rear.

From my reading I know I need to set the air screws about a half turn different front to rear.

Any advice on where to go from here?




Here is what we found the first time we tore into the carbs.

Air Screws 3/4 turn out front and rear
Jets 175 front / 178 rear
Pilots .50 front and rear
Needles 3rd Notch from top.

And to be honest I had tweaking carbs. I would rather pull the engine tear it down and rebuilt it than taking a carb apart.

Thanks,

I think there is not enough consistent data, with a full system it becomes allot more complicated to tune these bikes, especially with a stock motor.
Almost every bike will be a bit different tune then others, as such, a Dyno time would be best with some trial and error, which also would be the reason why many folks will not go full system, time and money.
If anyone knows better, correct me if I'm wrong, I would be glad to learn more as well.

I agree dyno time would be best but not possible right now.

The system was on the bike when I bought it and only got the factory cans without the factory header.

Set the pilot screws to 1 3/4 front and 2 turns on the rear. Pulls really good all the way through the rpm range but at constant throttle between 3,000 & 4,000 rpms it has a small surge.

Well as soon as my truck gets out of the shop I will be going back into the carbs again. Thinking I will go with 8541Hawks initial setup and work up from there.

I think you may need to use the 50 pilots. Though I have not had much experience with jetting a full system one of the guys here in the UK had a full Yoshi system and was constantly having problems with low speed stumbles and the bike not running right until he put 50's in. Also I believe the reason Factory Pro started supplying 50's is to cater for full systems and the reason the majority of us have to go with 48's with just the open cans and a factory pro kit.

I think the 180/182 mains should be OK, I would set the needles on the 2nd clip blunt end (so fairly lean) and use the 50 pilots. The fuel mixture screws would be around 1.5 turns out.

What air filter are you running and are you still using the standard velocity stacks?

If you go with Hawks carb set up including the smaller/standard mains you will have to put the needle on something like the 4 clip so a fair bit more richer than according to his set up by shimming the needles, which would counter act the leaner mains and pilot. If you go with the 48 pilots you will have to richen that up more than usual to around 3 turns. Whereas with Hawks setup they would usually be around 2.5/2.1/4

Either way I think blocking the extra lift hole and keeping the rear needle slightly richer is a good idea.

But to be honest once you have got what feels good you should put it on the dyno and see how things are and then tweak things accordingly.

It basically comes down to if by having the full system is it going to lean off the midrange or the top and bottom, and then you jet to suit.

(:-})

Thanks for the your input. Sounds like a good place to start.

I did have a K&N filter in but went back to the stock one. It ran ok with but just trying to see how it runs with the stock one. Also using the factory velocity stacks.

I hopefully will have my truck back this week then I will be able to work with the carbs some more.

Thanks again for your help and apologizes for not getting back to this thread that quick. Been one hectic week.

I tried the 48s pilots and found them to be too rich so returned to the stock 45's. This is at sea level and Tenn. is quit a bit higher so you don't need rich pilots sooting up your system and they will. Also the stock slides and needles are plenty rich enough for a K&N and I don't recommend using one, but only the stock filter. It's bigger than any 100hp engine will ever need, anyway. The heads on the vtr1000f flow enough air to make 100hp and that's about it so trying to rig the jetting to make more won't work.

I find it funny how there is so much advice given by people who have never run a full system exhaust on a SH.

I guess I'll go back to Attachment 15541Attachment 15541

:popcorn::popcorn:lol

Agreed...

And since I'm one of the few running a full system on a VTR (albeit a very non-standard VTR, and quite a different system... ) I'll offer up one piece of advice...

Disregard the above, and just put it on a dyno to get a baseline and work from there... I'm fairly certain I can't tell you how to set it up, but I can tell you that most of the guessing in this thread is wrong... I'd start with the 48 pilots, and round about Hawks baseline setup... But where I'd end up after testing is anybody's guess...

In a nut shell, as I said before, Dyno!!! Or you may never get it right.

From this I assume you don't want to spend hundred$ on a 'dyno dude' only to find yourself unhappy with the 'pro' results. Me neither. As for a full system header flowing better than the stock header, well, I'd like to see the proof and the only method of proof I know of is a dyno. That means getting a 'dyno dude' envolved and who's going to pay for that? If you don't try to hurry it the carb tweaking is easy.

As I'm kind of bored as my bike is still down I'll add a bit to my first post.

I didn't post earlier, as I have not jetted a bike with a Two Bandits...opps I mean Two Brothers header before.

Though I have done my fair share of VTR carbs on a few differently modified bikes.

So with that IMHO you are too rich on the mains right now. What kind of fuel mileage are you getting and what do the plugs look like?

Another thing to consider is that with a stock engine a full system is not free guaranteed power increase. In fact you might loose some HP or torque due to the header being larger than optimum size which allows the exhaust pulse to slow down giving the engine less scavenging.

They really are for if you up the compression.

So with that I would, like Tweety suggested, go to the carb set up thread I wrote.

Then do the slide mod, go back to stock mains, add 1 extra shim to the rear needle and drop them both 1 clip to the second from the blunt end and see how it runs.

You will be taking them apart a couple of times to get things dialed as the exhaust is an unknown.

The carbs are not that hard if you know the tricks, what part gave you trouble, I'm sure I have a easy way to do it.... ;)

As Tweety stated, "Very few true full-exhaust systems on Stock Superhawks."
And owning a s-hawk with the full system, I went back to 8541 post, and found a base-line the old fashion way(box of spark plugs, and 10 miles road) Two days later, Got the carbs close. Yet still not perfect.. will be put it on a Dyno..

HHHuuuuuuuHHHHH???

What happened to your bike?

I have a Yoshi full system, engine/filters/carbs are stock and it runs excellent, no stumbles anywhere. Would like to do the pair mod sometime to get rid of the off throttle burbling.