Beginning jet settings incorrect...2nd times a charm
 

ok..I rejetted my bike the other day with the following settings from the factory jet kit.
#175fr/#178r
needles at 2nd clip
2.5 turns on fuel screw
#50 pilot jets

when i used these settings when the bike was cold, and cruising from 3-4000 rpms the engine would missfire slightly. When the engine was warmed up cruising from 2-5000rpms the engine would missfire a lot.

at idle revving the engine developed no backfires and it sounded wicked.

the upper rpm band was powerfull cold and hot.

So i figure that the engine is still lean because of the missfireing.

Im thinking about these settings....

#178fr/#180r
additional 1/2 turn on fuel screws
2 clips on needles
#50 pilot jet

What do you guys think?

I think you'll end up too rich if you increase main jet sizes.

My basic rule for jeting is to change one parameter at a time, to isolate its effect.

#50 pilot jets may be too big, #45 seems about right on mine. Probably not a big deal as I still get a little lean popping when I close the throttle.

First I would raise raise the needles one notch (drop the clips) to try and get rid of the 3-4k stumble.

Re: Beginning jet settings incorrect...2nd times a charm
 

Good advice.
BTW,
I'm also running a #50 pilot that required a little more adjustment of the screws than I'd like... I may be installing some #45's... IMHO, Factory should include them with this kit...

I'm running a stock airfilter... may experiment with the BMC...
RC, your bike looks sick.

Dynojet doesn't provide pilot jets either.

I don't have direct experience with aftermarket filters. the advice I've been given is that the small gain in top end power is not worth the loss in the midrange that goes with it.

thanks. My bike has been a very satisfying project!

Re: Beginning jet settings incorrect...2nd times a charm
 

Yeah, that's what I've been hearing... I'm mostly just being lazy... overall the bike runs great at all throttle openings, but I think I'm probably a little rich.

Stock filter, Jardine Race Cores
Sea level, 80-85 degrees F

182, 185 mains
needle in 4th clip
50 pilot
1.5 turns out on the fuel screw.

It definitely looks rich on paper, but I also use the "one change at a time" method... started with the mains... 175, 178... 180, 182... 182, 185... just kept getting better... plug-chop reveals a real nice color. The improvement leveled off a bit with the change to 182, 185 so I could probably (maybe should) have run 180, 182 without being lean... Same deal with the pilot... 50 was better than the 45, but is probably a bit on the rich side... So, I could lean out the whole setup a bit (via jetting)... or... I could add a little more air to the mix (via BMC) and see what happens (lazy) :D

I dunno... I'm not in much of a hurry since the bike feels great "as is" right now and I really want to address the stock brakes and front end.

I expected the exhaust system to require bigger main jets, but left the jetting at 175-180, as it was. I was surprised to find that the bike was running rich. Dropped the main jets a size to 170-175 and it is much better. I live at altitude, so it makes tuning difficult.

But when I went to sea level it ran perfect. My friend on his 999R couldn't believe I only have 120 HP, because the VTR midrange is so strong. I was gapping him pulling out of corners in the twisties. The perfect street bike!

Seriously!
A modded vtr is an awesome bike... and a great sleeper. Every time I go out with new guys my bike gets no attention at the pre-ride meeting spot. At lunch it always has a little crowd after everyone has seen and heard it in action. I still have some work to do on mine, though. 120rwhp would be nice :D

Re: Beginning jet settings incorrect...2nd times a charm
 

Ok. I have some good and really messed up news.

Today I re-tuned my jet process on my bike and changed the settings on my needle clips from 2-3 and adjusted my fuel screws back to there original position which was 2 3/4 on the front and 3 on the rear. Hopefully this will make the midrange a little bit richer. At least i think it is running lean because it keeps missfiring in the midrange.

In the instructions it says if the engine has a "dry" flat spot at aproximately 3500 to 4000 rpm, raise the needle from 2-3. This will richen up the area.

And if the enigine has a "wet" rythmic, soggy spot at 4000 rpm that getts worse as the engine heats up lower the needle and lean out that area.

But what if my symptoms are both. I cant really tell because it just missfires.

When the engine was at idle the bike missfired a couple of times up untill i shut her down.

So my current settings are:
#175fr/#180R
needle at 3rd clip
2 3/4 turns on fuel screw front and 3 turns out on rear.
#50 pilot jet

This time it only took about an hour to do all the work on my bike but when I went to put the carbs back in the bike I STUPIDLY overtightened the front choke cable and it broke off in the carb.

So after a little bit of work I got the broken piece out of the carb and the 2nd broken piece out of my cylinder hole! Thank god the intake valve was closed and I ordered up a couple of new cables from honda.

So next week I will get to test out my settings. Damnit! I really wanted to go cruising tonight. :x

Ahhh.. The trials and tribulations of the home mechanic.

As a profeesor from China once told me "Learning is by doing, so here is your homework!"

Re: Beginning jet settings incorrect...2nd times a charm
 

Out here on the left coast I have:
Stock Mains
45 or 48(if the make it) Pilot
2.5 turns on both
Needle I forgot where

It took me 16 times to get it right using the seat-o-the-pants method. When I got it all right except for a slight stumble at 1/8 throttle around 4000-4500rpm I took it to get dynoed. Perfect Air/Fuel mix except for where I knew it was lean. If I were to change anything at all it would go out of whack so I left that tiny spot and regeared the bike so I dont have to use it anymore. My other option is to get the dynojet needle which Ive heard has a better taper on it but Im too lazy for that. 120 rwhp??? You have pistons and cams? Mine with Staintune Highs, K&N, Factory Jet kit and 2+Teeth in the back only posted 104hp and 67 or 76(forgot)torque. I still rape the Gixxer 1k's at the track :twisted:

Re: Beginning jet settings incorrect...2nd times a charm
 

Well I am still waiting on the choke cables to get in! Damn Honda. They were on backorder which I didnt learn from the delears untill yesterday. Freaking bitch! But I ordered the part on Bikebandit.com and paid extra for the shipping out here. So maybe Saturday I will get the part in. Untill then Im just twiddling my thumbs.

Re: Beginning jet settings incorrect...2nd times a charm
 

Finally!!
I got the valve for the choke cables in today and put my carbs back in and took it for a ride. Man! No missfiring, pulled wicked! and is smooth idling. I may have to raise the idle a bit because it is below 1K but it is sweet to finally be able to ride my bike and nothing bad happen :P

Final settings:
#175fr/#178R
needle at 3rd clip
2 3/4 turns on fuel screw front and 3 turns out on rear.
#50 pilot jet

These settings are with. K&N air filter, Exhaust Bafflectomy, PAIR disabled, Air box screen on left side removed.
Bike runs great and runs pretty cool. About midway on the temp gauge.

Re: Beginning jet settings incorrect...2nd times a charm
 

Any of you guys have a PDF, or other Doc style file, of the DynoJet instructions? My VTR had a kit when I bought it (used /w 2000mi). I have leftover jets, but no instructions! It runs well, with Yosh Ti slip-ons and a K&N, but if I want to make changes I have no idea which way to go?
Thanks, even a Factory set of instructions would help.
:?:

If it runs well, don't mess with it.

Re: Beginning jet settings incorrect...2nd times a charm
 

First...I dont have my scanner so I cant scan the Factory instructions in for you 102dals

Secondly back to my jetting...
I was wrong in my assumption that I had it all figured out. I dont yet. At idle the engine sometimes just dies. Why does it do this? Is it too lean, to rich? Whats it doing. Do I need to adjust the fuel screws?

thanks

Justin

Re: Beginning jet settings incorrect...2nd times a charm
 

It isn't that I want to mess with it... I just want to know what they are, and what they should be.
I've changed jets a million times on my 88 Hawk GT, and I know it's the same procedure. The carbs even look the same.
Anybody?

When I had the Factory #50s in it, I couldn't make it idle reliably with any jets/clip/screw settings. Had to fall back to the #45s.

On the plus side, if anyone in Florida needs their carbs pulled, I've gotten quite profficient at it... :)