Another Jetting Thread

[jscgdunn]

Hi Everyone,
I have a 92 with Supertrapp pipe (4to1, 10 discs) and pods (ie 3ZX14W bike).  We are 3500 to 4500 feet elevation here in Bragg Creek.  It ahs 18 38 gearing.

In comparison with my 89 FJ (stock exhaust and airbox) with same gearing...the one with pods and pipe is not near as strong. 

Bike was good before pods and pipe. Both have about 75000 KM. 

Currently have 112.5 mains and 40 pilots.  Stock needles in mid position.  No bogging or flats spots down low.  Starts/idles/runs good.  Carbs are clean. 

Low end is ok but does not pull hard on mains at all...ie no kookaloo....will not pull to redline in 4th.

Spent a bit of time researching and I understand it is an iterative process starting with the mains and working the process as here:

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

The starting point is the tough part to figure out as I do not have a selection of jets. So I gathered up the data I could find:



Hopefully you can open this picture and blow it up a bit.
(This might be a good chart for the files section if we could complete it a bit, so if there are corrections or other examples to add let me know.)

It looks like the FJ1289 bike with the supertrapp might be most similar.

Any advice welcome before I go to Randy for jets!

Thanks,

Jeff



Any advice welcome.

[a.graham52]

7will adding slight amount of choke make it run with more power? If so this just confirms you need to go richer. Start with just a tad of choke at first as to not over do it and give you the wrong idea

[jscgdunn]

Randy was a big help here.  I have ordered 117.5 and 120 main jets and 42.5 pilots.  Will update.

Jeff

[ribbert]

I have run 117.5 mains for a long time and never had reason to question it, the bike pulling well right through the rev range and gears.

I wring my bike out often enough in high gears to be familiar with what it feels like.
Some time back I did just this and was surprised how much harder it was pulling to 9000rpm in 4th, and continue to accelerate in 5th. I had made no changes to the bike and environmental factors played no part. The only thing that had changed was the uni filters were literally splatted with mud and putrid with talcum powder fine outback dust.
I cleaned the filters and could feel it had lost that edge off it's high end punch.

I fitted some donated 122.5's (thanks Pete) and it pulled like a train again.

Just an observation.

Noel

[jscgdunn]

Thanks Noel,
What are you running for pilots?
Mixture screw setting?
Clip position?
Float height?
What elevation do you typically run at?
Exhaust?

Thanks,

Jeff

[ribbert]

Thanks Noel,
What are you running for pilots?
42.5

Mixture screw setting?
By ear, not sure how many turns.

Clip position?
Raised 1 notch

Float height?
Don't know. I set them 7 years and many miles ago and haven't touched them since.

What elevation do you typically run at?
Sea level to 1000'

Exhaust?
Delkevics, baffles in.

Thanks,

Jeff

Jeff, I have answered your questions because you asked them but I would never put forward my carb set up as a model of good tuning. As long as it's running well, I don't touch it (that goes for the whole bike, other than the most basic maintenance). My carbs have only been apart once in 125,000km.
I do balance them probably once a year but they're never far out.
We are blessed with good fuel here and I have a filter.

Noel

[jscgdunn]

Thanks Noel,
I am trying to put the list together of what works for everyone is there is a good starting point for jetting if the typical small modifications are made from stock...ie no airbox and non-stock exhaust.

Jeff

[fj1289]

When you are comparing main jets sizes that work well for people you MUST relate that with the needle being used!!!!!!!

A stock needle with a 115 main jet could be a richer setting than a factory pro needle with a 125 jet!  I'm pretty sure factory pro uses "fat" needles that require a larger main jet size than a stock or dyno jet needle would require.   

When I put a factory pro kit in my carbs several years ago I called and talked to them since I was at 4600' elevation.   I talked with them about the main jet sizing since it seemed way too large for a stock motor with bolt-ons -- especially compared to what had worked well at sea level.   He explained the difference the needle design makes with he main jet -- even at WOTwhen you are "off" the needle.  That was another case of learning something I didn't know I didn't know..... something that keeps happening ......

[fj1289]

Hi Everyone,
I have a 92 with Supertrapp pipe (4to1, 10 discs) and pods (ie 3ZX14W bike).  We are 3500 to 4500 feet elevation here in Bragg Creek.  It ahs 18 38 gearing.

In comparison with my 89 FJ (stock exhaust and airbox) with same gearing...the one with pods and pipe is not near as strong. 

Bike was good before pods and pipe. Both have about 75000 KM. 

Currently have 112.5 mains and 40 pilots.  Stock needles in mid position.  No bogging or flats spots down low.  Starts/idles/runs good.  Carbs are clean. 

Low end is ok but does not pull hard on mains at all...ie no kookaloo....will not pull to redline in 4th.

Spent a bit of time researching and I understand it is an iterative process starting with the mains and working the process as here:

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

The starting point is the tough part to figure out as I do not have a selection of jets. So I gathered up the data I could find:



Hopefully you can open this picture and blow it up a bit.
(This might be a good chart for the files section if we could complete it a bit, so if there are corrections or other examples to add let me know.)

It looks like the FJ1289 bike with the supertrapp might be most similar.

Any advice welcome before I go to Randy for jets!

Thanks,

Jeff



Any advice welcome.

Jeff - for these settings with the Kerker pipe - that was close to sea level when I lived in Florida. I think we finally figured out those carbs had dyno jet needles and slide springs with Mikuni main jets - so a bit mix-n-match.   The supertrap settings were a complete factory pro kit with new emulsion tubes and were set up at 4600' elevation in New Mexico.  Also - that supertrap pipe wasn't the stainless steel version it was a mild steel supertrap header mounted to an unknown supertrap  muffler section that happened to fit the FJ well by adding a short adaptor at the end of the collector. 

[jscgdunn]

Thanks. I saw the jet cross reference charts as well.  Mixing and matching would really complicate matters I think.

I am sticking with mikuni needles jets.   My goal is to get back to equivalent performance to stock.

Does your bike the supertrapp have FP jets as well as needles?

Thanks for the tip,

Jeff

[jscgdunn]

Hi Everyone,
I have a 92 with Supertrapp pipe (4to1, 10 discs) and pods (ie 3ZX14W bike).  We are 3500 to 4500 feet elevation here in Bragg Creek.  It ahs 18 38 gearing.

In comparison with my 89 FJ (stock exhaust and airbox) with same gearing...the one with pods and pipe is not near as strong. 

Bike was good before pods and pipe. Both have about 75000 KM. 

Currently have 112.5 mains and 40 pilots.  Stock needles in mid position.  No bogging or flats spots down low.  Starts/idles/runs good.  Carbs are clean. 

Low end is ok but does not pull hard on mains at all...ie no kookaloo....will not pull to redline in 4th.

Spent a bit of time researching and I understand it is an iterative process starting with the mains and working the process as here:

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

The starting point is the tough part to figure out as I do not have a selection of jets. So I gathered up the data I could find:



Hopefully you can open this picture and blow it up a bit.
(This might be a good chart for the files section if we could complete it a bit, so if there are corrections or other examples to add let me know.)

It looks like the FJ1289 bike with the supertrapp might be most similar.

Any advice welcome before I go to Randy for jets!

Thanks,

Jeff



Any advice welcome.

Jeff - for these settings with the Kerker pipe - that was close to sea level when I lived in Florida. I think we finally figured out those carbs had dyno jet needles and slide springs with Mikuni main jets - so a bit mix-n-match.   The supertrap settings were a complete factory pro kit with new emulsion tubes and were set up at 4600' elevation in New Mexico.  Also - that supertrap pipe wasn't the stainless steel version it was a mild steel supertrap header mounted to an unknown supertrap  muffler section that happened to fit the FJ well by adding a short adaptor at the end of the collector. 

Our posts crossed.....

[ct7088]

I'm at 1200 foot in OKC. 85 FJ 1100 UNIPODS another Non stainless SuperTrapp with 13 disc. Just changed to 17/40 from 17/41 with GSXR rear wheel change. Randy recommended 112.5 to 115 main jet and 40 for the pilot and to try a spacer under the non adjustable needle. I'm using the 115 main and haven't tried the spacer but i expect to try them in the near future. Pulls hard it seems to me. I have the dregs of a Factory Pro Jet Kit that only gave me grief. Factory Pros answer was that the humidity in Oklahoma was to high. they sent different needles but it didn't help.

Chris

[FJ_Hooligan]

With pods and an exhaust, you definitely need to install the needle spacer.

[ct7088]

OK and Thanks

Chris