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Discussion Starter · #1 ·
A While ago I rejected my TBS (kehin carbs) and adjusted the needle to fit the K&N filter and TOR pipes. The bike now runs great and pulls much harder on all rpms. However it now has some starting issues. It more difficult to start now and it was not a big deal but now when the weather became quite colder (again) the issue is worse.
First the bike does not start and when it starts it dies because it can’t rev up. After several tries it finally idles but I cannot add any gas as long as the choke in engaged. When I drive away I have to wait for the idle to reach 3000 rpm (with the choke fully engaged) and then turn it off and give gas. The bike first dies but starts again immediately when I apply gas. I guess this might be fixed by adjusting the pilot screws, but can some tell me how to do it? They are now 2½ turns out.
Or might there be any other issue that I have overlooked?
 

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2.5 turns should do it. what size pilots are you running?
 

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Discussion Starter · #3 ·
it's the originals, 38, and i didn't change 'em. The bike started fine before I changed the mains and adjusted the needle, and I could go all the way to work with full choke (if I forgot about it). Now I cannot apply even a little bit of gas as long as the choke is in.
 

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I've got my screws 2.5 turns. The jet kit came with #40 pilots but I ended up going with #42 because of my particular setup.

My suggestion would be to try it with the idle screws out to 3 turns and if that doesn't help then go back to 2.5 turns and install the #40 pilots.
 

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With a stock airbox and K&N #40 pilot for sure.
 

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Discussion Starter · #6 ·
Ok, the jet kit didn't include any pilot jets, so I'll try three turns on the screws first. I'll probably won't get into it untill tomorrow evening.
 

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Do not go any more than 3 turns out on the pilot screw or you may find that it will fall out of its own accord.
 

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"After several tries it finally idles but I cannot add any gas as long as the choke in engaged."

What did you do to the needles?
You say you adjusted them.
 

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Discussion Starter · #10 ·
What did you do to the needles?
You say you adjusted them.
Actually I installed a Dynojet kit. With 104 DJ mains (107,5 kehin) and a Dynojet needle in the second notch according to the instructions. However the DJ needles looked quite similar to the ones already installed but they were on the top notch, so I assumed that DJ needles already were installed. I switched them anyway to be sure.
 

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I'm a little surprised you're using the largest jets of the DJ kit having only installed a K & N filter. When I did this, I ended up back on the stock jet. The needle has a very steep taper, so small changes in jet size can have big results at the start of the taper. I tried, just for an experiment, once, to make the needles just one 'clip' richer - the bike stalled completely coming off tickover. Went 100m & limped back. Would start fine, but simply would not go above 1500/2000 rpm at all.

So....what I'm thinking is this....

You have left some small gaps where the two halves of the airbox join when you fitted the K & N. The jetting is incredibly sensitive to this because the air intake is so restricted to begin with.

So...the main jets are more or less coping with the situation, but the pilots are not. And I wonder if they could do with a clean out too?

Options...

Sort out the airbox & refit smaller mains (1 size up max IMO) & clean the pilot jets thoroughly or fit new ones one size up (40) anyway.

Or...
Leave as is & fit new pilot jets either size 40 or 42.

Why I think this may be relevant...
I helped a guy with a Tbird swap out an old knackered airbox once for a new one. The old airbox had not been modified in any way, but the bike had been rejetted with 120 mains & initially I couldn't see why. Well, the bike ran like sh1t, so we took another look at the old airbox. Then we noticed how the joint of the two halves had become distorted and there was actually only a small gap but for a very long length of the seam/joint.

The fix was to leave the jetting alone but drill an extra intake hole, in the new airbox (on the other side, of the same diameter as the original ~38mm IIRC). Bike then ran perfectly.

So the moral of that story is...if the airbox is not properly & fully sealed, it will cause big fuel mixture problems. (Maybe that's partly why Triumph don't want us changing filters but buying new boxes?)
 

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But Mike, one of the things he mentions is that the choke (enrichener) will kill the engine. I'm thinking he may be way rich to start with.
The needle and main is what have me thinkin'.
On a stock airbox #40 pilot and one size up on the main I found right on. (I think it was #101).
But that needle.......................
 

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Yeah, I see what you're saying there, but I'm not too sure about the exact operation of the choke? I tend to think it's a bit 'all or nothing' for starting, you know how it tends to over rev wildly at some point with it? So maybe it's a case of initially not enough & then way too much?

Could be wrong there, but I was trying to tie in with the recent mods he's made with airbox & DJ kit, & what could go wrong with that.

But a bit mysterious eh?
 

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Discussion Starter · #14 ·
But Mike, one of the things he mentions is that the choke (enrichener) will kill the engine. I'm thinking he may be way rich to start with.
The needle and main is what have me thinkin'.
On a stock airbox #40 pilot and one size up on the main I found right on. (I think it was #101).
But that needle.......................
Sorry for not being 100% clear and I’ll try to clarify. I have to have full choke when I start. When its really cold outside (under 10 C) the bike will start but cannot idle because it only reaches 100- 200 rpms. Each try raises the revs so it finally after several tries idles at about 500 rpm and then I’ll only have to wait for the bike to reach 3000 rpm before I can take the choke away and apply gas instead.

When warmer outside the bike idles at just below 1000 rpm from the start so the problem is quite smaller but still…
 

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Discussion Starter · #15 ·
I'm a little surprised you're using the largest jets of the DJ kit having only installed a K & N filter.
The dynokit recommended the 1o4 Dj mains for K&N air filter, TORs and with the foam insert in the primary air box taken away, so that’s why I chose them.

You have left some small gaps where the two halves of the airbox join when you fitted the K & N. The jetting is incredibly sensitive to this because the air intake is so restricted to begin with.
Yes, that makes good sense. I was surprised by the addition of power for just changing the air filter. A less restricted air box might explain that. I guess it’s hard to go back....
However, did not have time to pull the carbs today so I just tried the pilot screw but that didn't do anything at all. I tried a lot of positions from 2 turns to 3 turns out and I could not see any difference. Hope I can find some bigger pilots tomorrow.
 

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Discussion Starter · #16 ·
At the lokal Triumph store I was told that Triumph do not suply other Pilots than 38:s.:confused:
I managed to find a pair of used 42 at another dealer, hope they will fit. The 40 and 42 polits are rare they told me and they wanted about 10$ each for the used pilots. They are now in cleaning and I will fit them later tonight. A full testride will have to wait since its heavy raining today.
 

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Discussion Starter · #17 ·
42 pilots are in place and bike started up just fine. Went for a short spin and the bike is going terrific, perhaps just a tad rich according to the plugs and a tad drop of hp at the very top end. You guys are great, thank you for all help. I’ll never stop being amazed over your skills Mike.
Is there any other way to notice if the bike are going just a little rich/or lean than pulling the pluggs?
I guess riding with a gap in the air box is not the best way or can I be 100% sure the air does not slip in passing by around the filter in some way? I guess the filter is on the inside and its working fine but anyway it would feel better (or more in control I guess) to have the air box sealed and add an extra hole instead. That has to wait since I’m pretty tired of having the carbs. out right now.
Am I right if I conclude that it is the most usual setting to have 120 mains with an extra hole, same sized (38mm) on the opposite side, of the original one in the secondary air box?
 

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An exhaust gas analyser that dyno shops usually hook up whilst measuring power/torque is the most usual way of checking rich/lean conditions, besides checking plug colour.

I'm running 115 mains with the extra hole & I met a French guy once using 120s & 120s seems a more common go generally. I have dynojet needles, so I could be a tad lean wide open maybe, but don't notice much because I'm not there often & the needles maybe compensate a bit. I've been meaning to try 118s or 120s some time & even get it to a dyno, but haven't got round to it as yet!

Yes, I think in due course, it would be best to know exactly how the airbox is performing, then everything will work consistently if it's ever replaced?
 

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You may want to drop the needles a notch and 2 turns out on the idle screw to compensate for the 42 pilot.
But as Mike says there's no substitute for an air/fuel meter.
 

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By the way, it's time to sync the carbs if you haven't already done so.
 
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