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91 1100M with Akrapovic 4-1, Dynojet stage 1 and K&N airbox filter


Nick

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Hiya,

Got the above set up with standard BST40 carbs, which have been ultrasonically cleaned and rebuilt with new emulsion tubes, o rings and float valves.

I've ended up putting a dynojet stage 1 kit in the carbs as it was always quite lean with the pipe and filter, but can't getting it running right with their recommended settings.  The airbox has a k&n panel filter in it, but has the thicker, more restrictive velocity ring in it at the moment...

I'm getting pissed off pulling the carbs on and off, and appreciate it needs dyno testing but it's not even rideable to get there as is.  Does anyone have a similar set up on this bike and who what their settings are?  Are people running the less restrictive ring in the airbox with these stage 1 kits...?

 

Thanks

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I used to have the same set up minus the dynojet kit (GSXR 1992), standard jets and the small inlet rubber .

I read  here somebody opened the small inlet rubber 3mm in a lathe because he couldnt get the bigger one to work , i dont remember the thread though .

Sorry for asking a stupid question but you balanced the carbs right ?

 

 

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The kit comes with DJ122 and DJ126 mains, and states to use the 126's for an aftermarket exhaust.  I know the sizes aren't apparently comparable with Mikunis...

Yep, carbs were balanced up...

Edited by Nick
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snippet

Had 150 m.jets until 2 months ago when I found that the milder conditions/longer rides left my bike feeling a tad rich, so I fitted mikuni 145 mains.

So this is my set-up arrived at over time - it might help anyone who has a similar set-up as my bike 1100M or N, big bore, flowed head, full system and std airbox with a higher flowing filter - these are the carb settings I ended up with (bikes vary a bit, but it should be close)  std float heights, 145mains, std needle on 3rd and 37.5 pilots - pilot mixture screws 2 1/3 out - still surprised how much leaner all these settings are compared to my bike as a 1127. The pilot settings mean the bike is cold blooded for 2 miles and then clears up, the clean running low down was always the hardest thing to correct, the bike carburates perfectly when up to temperature now. The size of main jets do seem to bleed lower down too, I've done loads of messing about and they always make a difference to the 40mm cv carbs, which seem to show up any changes compared with many

 

although he has a big bore kit, there is tons of info in there and hopefully this might get you in the ballpark

Edited by baldrick
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150 to 160 mains are used when stg3 .. easiest thing to try is tape up half the velocity ring and see if better ( less air ) or remove and see if better , will give you an idea of which way to go … how good are your float bowl gaskets ??? And what’s the float height set too .. ? 40mm carbs are no worst to set up then any others .. and which way round is the velocity ring ?? 

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If using an air fuel machine you can get the best from them. I agree they are a little large .. but always had great results on dyno . Stg 1 worked better . Could 4th gear roll on from 2k no issues  and I’ve never seen smaller then 150 in a stg 3 . Ran a dyno for 10yrs . So wasn’t guess work 

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2 hours ago, Gixer1460 said:

You are probably in a minority of one with that statement! Jet sizes you advise are masking how badly the carbs are working!

Also many other factors.. exhaust can determine very different jet sizes for a stg 3 kit .. I can only talk from my experience.. 

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14 hours ago, Serafumi said:

150 to 160 mains are used when stg3 .. easiest thing to try is tape up half the velocity ring and see if better ( less air ) or remove and see if better , will give you an idea of which way to go … how good are your float bowl gaskets ??? And what’s the float height set too .. ? 40mm carbs are no worst to set up then any others .. and which way round is the velocity ring ?? 

Float bowl gaskets are brand new viton, and the float heights are standard.  

It has the more restrictive ring in with the 'chamfered' part facing out towards the back of the bike.

Using their settings, the bike stumbles around 3 - 4k when rolling on, so my guess is that it's too rich, though moving the clip up the needle to lower it and lean it out means that it doesn't pull well above 5k.

I always thought these kits were supposed to be somewhere near rideable as a drop in solution?

I'm gonna swap over the velocity ring to the less restrictive one and see what happens...

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The kits should certainly be somewhere in the ball park .. if one clip position makes that much difference. Try putting a dynojet shim under the clip , that will give you half a position .. and I found that having the velocity ring taper out worked well .. mixture screws around 3t ? 

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most of your running will be on the needles, if you've got a stable tickover and a half decent needle position you can ride it and figure out if any of the circuits need to be leaner or richer. I take it the dynojet kit came with needs and emulsion tubes ? if you use their needles, you have to use their emulsion tubes and vice versa, else it's near impossible to tune.

Altering needle position is pretty easy, try a notch higher and lower, the engine should like one or the other more. Early in my ownership I had a k and N in the airbox and an Akra - I used  130 mains, std needles lifted 1 notch and pilot mixture screws out an extra half a turn..... obviously you have a DJ kit so sizes will be different, but the process will be similar. The good thing about using an Akra is that you know they're developed to deliver a smooth delivery, so that's one known, it won't be at fault. 

Does the bike run okay at any revs and throttle ?

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On 8/5/2022 at 12:10 AM, Oilyspanner said:

most of your running will be on the needles, if you've got a stable tickover and a half decent needle position you can ride it and figure out if any of the circuits need to be leaner or richer. I take it the dynojet kit came with needs and emulsion tubes ? if you use their needles, you have to use their emulsion tubes and vice versa, else it's near impossible to tune.

Altering needle position is pretty easy, try a notch higher and lower, the engine should like one or the other more. Early in my ownership I had a k and N in the airbox and an Akra - I used  130 mains, std needles lifted 1 notch and pilot mixture screws out an extra half a turn..... obviously you have a DJ kit so sizes will be different, but the process will be similar. The good thing about using an Akra is that you know they're developed to deliver a smooth delivery, so that's one known, it won't be at fault. 

Does the bike run okay at any revs and throttle ?

Thanks.  Strangely enough, the brand new DJ stage 1 kit didn't come with replacement tubes and there is no mention in the instructions of them - the DJ jets just thread into the mikuni tubes.  Odd, because I was always led to believe that DJ used their own emulsion tubes, but clearly they have changed.

I believe it's too rich on the needle, as lowering (as in putting the clip in the higher slots) it helps with the 3.5 - 5k stumble and bogging.  Trouble is, lowering it also kills the 6k + acceleration.

When you had a K&N, were you using the less restrictive airbox ring?

It ticks over ok and revs cleanly from idle, but when riding it, the issue becomes apparent.  I've also tried raising the needle but that was fouling plugs, which leads me to think the MJ is possibly too large in the first place...

The kit didnt come with pilots and i've left the stockers in there.

 

 

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Well, I changed the air filter ring for the less restrictive one and put the needle clip back to the 3rd one down.

Bike would only run on choke at first with the pilot screws at 2.5 turns, so put them at 3 and a third to get a decent idle without it 'hanging.'

Took the bike out for a ride and the roll on is pretty good in top from 3k, so I guess the kit was always designed for the filter without the 'plugging' ring in.

I may drop the clips one on the needle to see if it pulls any harder, but it's really quite good as is...

 

For future reference for anyone else who needs settings:

1127M with K&N filter in airbox and less restrictive ring (chamfer to rear of bike)

DJ stage one kit - DJ126 main jet, needle clip 3rd from top, pilot screw at 3 1/3 turns out.  Slides drilled as per instructions...

Thanks for all the help guys...

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On 8/6/2022 at 2:28 PM, Nick said:

Thanks.  Strangely enough, the brand new DJ stage 1 kit didn't come with replacement tubes and there is no mention in the instructions of them - the DJ jets just thread into the mikuni tubes.  Odd, because I was always led to believe that DJ used their own emulsion tubes, but clearly they have changed.

I believe it's too rich on the needle, as lowering (as in putting the clip in the higher slots) it helps with the 3.5 - 5k stumble and bogging.  Trouble is, lowering it also kills the 6k + acceleration.

When you had a K&N, were you using the less restrictive airbox ring?

It ticks over ok and revs cleanly from idle, but when riding it, the issue becomes apparent.  I've also tried raising the needle but that was fouling plugs, which leads me to think the MJ is possibly too large in the first place...

The kit didnt come with pilots and i've left the stockers in there.

 

 

Sorry for the delay, I've been fiddling about on another little project. My k and n was fitted when I bought the bike and a previous owner had hacked around  the inlet with a knife !!  I trimmed a yoghurt pot and siliconed it in the inlet, this gave a 50mm orifice and a radius going into it. 

It sounds like you may need to go up a size on the pilots, but if the idle and gentle cruise are okay, leave it until you have enough time to remove the carbs again - it's a bit of a pain removing them with the airbox.

If you can find a decent setting with DJ needles and std e.tubes don't question it !  Dj needles have a different taper to the std needles,  so probably will go rich quickly. Go with what the engine likes, I wasted a fair bit of time over thinking the jetting.  Also make sure the engine is fully up to temperature when settling on the jetting,  several times I thought I'd sorted everything and then went on a long ride and my 'wonderful ' carburation... wasn't so great.

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