Rejet

[Bota58]

I just put Cobra pipes on this fall,pulled the carbs and put in 38 slows and 108 mains also new float needles,all new silicone vaccuum lines as well and it has a K&N air filter without the pre filter.I took it to the dealer after to get the pilots adjusted and carbs synced also checked valves but now the problem is a big flat spot on high end at 65-70 when you pull on the throttle and it just sits there and slowly builds speed not like it used to be when you had to hang on.It is a 99 I/S with a 4 degree timing wheel and stock air box,any suggestions.It ran a lot better with the stock jets and Cobra pipes than it does now with the new jets.
Thanks

[Patrick]

I'd recommend going over what the dealer did. I see no reason for 108 jets, the original 100's run a bit rich. With 38 low jets the pilots should probably be set at 1.5 to 1.75 turns [ 2.25 for 35s] and you can do that without much trouble. Get yourself a vacuum gauge and all the related junk and adjust the carburetors yourself. If the dealer did have the valve covers off, I'd take them back off and check the adjustments. Do you think I trust dealers ?

[Bigwolf]

I'd recommend going over what the dealer did. I see no reason for 108 jets, the original 100's run a bit rich. With 38 low jets the pilots should probably be set at 1.5 to 1.75 turns [ 2.25 for 35s] and you can do that without much trouble. Get yourself a vacuum gauge and all the related junk and adjust the carburetors yourself. If the dealer did have the valve covers off, I'd take them back off and check the adjustments. Do you think I trust dealers ?

+1

I had my Valk for only 800 miles when it was time for the 20K maintinence.  I took it to the dealer and asked that they also check valve clearance since I had accidentally hit the rev limiter a couple of times.  Bad choice!  For my first 800 miles the bike was a screaming demon.  If I did not bang the first 2 shifts almost as quik as I could, I would hit the rev limiter.  Even with wife on board and we are not lightweights.  When I got it back from dealer, it was really lazy .....I could twist the throttle in low gear and have to wait and wait for it to get enough revs to shift to second even with just me on the bike.     The bike also ran much hotter than before and the cobra 6x6s were soon blued twice as far back. 
I do all of my own work now.  Never again will any dealer touch my bike.  There may be some good dealers out there but it is just not worth the hassle to me.

Bigwolf

[Momz]

The 108s are waay to rich. What made you believe that you needed to change the main jets?

Like it's been stated on this forum board; don't take your bike to a dealer,.....ever!

This Tech board is a wealth of information and we can guide you through your issues, whatever they may be.

[art]

I'd recommend going over what the dealer did. I see no reason for 108 jets, the original 100's run a bit rich. With 38 low jets the pilots should probably be set at 1.5 to 1.75 turns [ 2.25 for 35s] and you can do that without much trouble. Get yourself a vacuum gauge and all the related junk and adjust the carburetors yourself. If the dealer did have the valve covers off, I'd take them back off and check the adjustments. Do you think I trust dealers ?

Got to agree, the only mechanic or dealer I trust is myself and if I screw up I don't have to pay again I just do it again until I get it right. I've been screwed to the tune of $1000 by socalled mechanics on carb work. Never again. Auto shops are just as bad.

[Bota58]

I went by lamonsters write up when I changed the jets he actually recommended using between 105s and 110s but said you could start in the middle with 108s so that's what I tried.It did seem to run pretty good with the stock jets but it seemed like everyone I talked  to recommended changing jets with the cobras and since the bike had been setting for about a year when I bought it I figured the carbs needed cleaning anyways and I was right the were pretty dirty.I guess if I can't get it lined out with the jets that are in it now I may have to put the stock mains back in or at least go to 105s
Thanks for the response and keep ideas coming if there's anything else I could be missing.Yeah I'm not too happy with the dealer as he told me it was running fine when he called me to pick it up.
Thanks

[salty1]

I'd recommend going over what the dealer did. I see no reason for 108 jets, the original 100's run a bit rich. With 38 low jets the pilots should probably be set at 1.5 to 1.75 turns [ 2.25 for 35s] and you can do that without much trouble. Get yourself a vacuum gauge and all the related junk and adjust the carburetors yourself. If the dealer did have the valve covers off, I'd take them back off and check the adjustments. Do you think I trust dealers ?

Did the dealer synchronize your carbs? If not, get that vacuum gauge and do what they should have done. You can do it. Lots of how to posts here.

[Bota58]

Yes they supposedly synced the carbs adjusted pilots and checked the lifters and called me and said it was running fine.I called them today to complain and they told me it had been too cold for them to test ride it much,kinda made me wonder why they called and said it was done if they hadn't test rode it.But it does sound good at Idle or when you're revving at stop but under load it is just flat.
Thanks

[R J]

1st off, my experience, is you do not have to rejet for the Cobra 6X6's.

It might not top out on the top end as fast as before the exhaust change, but it will get there a hell of a lot quicker.

1st thing to do, is go back through those valves.   Sounds like maybe the exhaust are too tight.

Then reset your idle screws to, from memory here, 2 1/2.    If that isn't correct, someone will let ya know.

And while you are messing with the idle screws, change the fast jets back to 105's.

Come back and let us know how it runs after these changes are made.

The bike should not shudder at any speed in any gear.

It should wind out to the limiter real fast like.

[Patrick]

I'm also thinking that if anything after putting it back to original you might just shim the factory needles a bit. That usually corrects anything related to aftermarket exhausts.

[salty1]

My 97 had Cobras and ran like a scalded dog with stock jets. The only thing that changed was the pilot screws were set at 2 1/4 turns out and a K&N filter with the preform was used.

[Bota58]

So what's the general consensus,should I go back to stock mains or go to the 105s,I just want to get it going soon as the weather is changing fast.
Thanks

[Blackduck]

Being one of the crazy's who has done a lot of messing with the air box and have a pretty good handle the way these lovelys fuel I would go back to the stock jets and if by sparkplug readings you are lean go with a shim under the needles as per Patrick's comment.
Standard air box will run fine to around 3000 rpm then start to richen the mixture, larger jets compound this. Max I would go with jets and a stock airbox would be 102's
Have a buddy follow you and see if there is dark smoke from the exhausts when you hit the flat spot.
Added timing will not help with rich mixtures.
Cheers Steve

[uturn]

i concur. i run stock box with k and n no foam, tbrs straight 6x6's, started with stocks reemed out a little, it was super lean low end. went to 38's and that seems to be good all the way through

[salty1]

Go back to the 100s and leave the 38s in, pilots at 2 1/4 turns out, and resychronizing your carbs. FWIW

[Bota58]

Yeah I just want to be sure it's right this time as I put the bowls back on with new gaskets and the factory glue and the weather is warming up.
Thanks

[Bota58]

I've got the d tool but what else do you use to adjust the carbs,possibly 1/4" ratchet?
Thanks

[salty1]

Externally, the adjustments would be the pilots @ 2 1/4 turns out, synchronization screws and the idle knob. A D-shaped tool and a screw driver. 

[Bota58]

The D shaped tool I have is just a bit that's why I was wondering what do you put the bit in,nut driver style or ratchet as there's not a lot of room.
Thanks

[Patrick]

If the carburetors are installed you can remove the intakes if you feel the need for more room. I remove the pilots and slot them for a normal flat screwdriver and add a dab of never-seize to the threads.
Setting for the pilots, 35s- 2.25 turns, 38s- 1.5-1.75 turns. Aftermarket exhaust may take the pilots being set a bit richer.
Sync the carburetors. I recently posted the procedure for another member.

[Bota58]

Yeah it's got 38s and cobra pipes and I'm going back with stock mains.
Thanks

[salty1]

Bota58, the D shaped tool is female. It usually can turn pilots only using your fingers to twist it.  ???

[Bota58]

Has anyone tried to rejet the barbs without taking them completely off.
Thanks

[salty1]

Barbs = carbs?    Some have but it much easier and probably wiser to remove the carb bank.

[Bota58]

Yeah so much for auto correction,Yes carbs

[Patrick]

Has anyone tried to rejet the barbs without taking them completely off.
Thanks

Yep, easier and faster as far as I'm concerned. Others will disagree.

[Bota58]

Ok so I'm ready to pull the carbs back off tommorrow and put the stock mains back in and I'm gonna leave the 38 slows in so is everybody in agreement that the pilots need to be about 2 1/4 turns out,I just want to try and have it right this time also I'm putting a Dan Marc fuel valve on while I'm in there.any advice would be appreciated.Thanks in advance.

[R J]

On the Dan Marc, make sure there is NO uphill on the exit hose to the carb fuel rail.

[whitestroke]

I think the norm would be 1.75 turns on the pilots with 38's.

[uturn]

+1 screws 1 and 3/4 turns out for 38's and stock mains with open pipes

[Bota58]

Yeah I forgot to mention I'm running cobras with baffles.I didn't know for sure how rich it needs to be
Thanks