V&H 4:1 & K&N Inbox - suggested jetting

[KEITH KRAUSE]

Yes, in your case, the bike would be running lean on the pilot circuit and jet needle.
As for the main, it's the SMALLEST opening in the combined jet needle/main jet circuit that controls fuel flow.
The fuel first enters the main but the space between the TAPERED jet needle and needle jet is smaller at any throttle position less than 3/4. As the needle rises up through the needle jet, the thicker portion actually leaves the jet needle area and the lower/thinner portion comes into effect more and more. As the needle rises, the space between the two parts becomes larger than the opening of the main jet. At that point the main now controls flow because it is the smallest opening in the entire circuit.
As you can see, the tapered needle is designed to make a smooth/gradual transition to the main jet.

[mcneilk]

thanks for the explanation. i will move the needle position before riding.

anyone have a good site to order jets?

[twr1776]

You can still order the Mikuni OEM jets from Parts Unlimited, or others. I ordered pilots from PU last year and they were about 2.50 each as I recall. There are a lot of posts here on bad aftermarket jets.

[salty_monk]

So I went with the V&H. Looked at the Jardine 4:2 set I had, they would fit but more hassle & I couldn't be bothered!! Want to ride.

Ended up with Mikuni 122.5 main, Canadian Needles Up one notch, air jets are 180's, pilots are 40's. Screws out about 2.5 turns. Floats set to bang on stock, both sides etc checked with a vernier.

Short run today, different bike, much smoother, will pull better through all the gears, do things in third it wouldn't have wanted to do before etc.

Couple of things....

1. There is just a "hint" of "popping" when on overrun, I figure this might be normal with the V&H can

2. If I really gun it & open up the throttle too quickly in 2nd gear I get a backfire through the exhaust (doesn't happen if I am more progressive with the throttle).

One thing I should note, the gas is at least a month old in there & has some "sea foam" in it plus maybe remnants of carb cleaner etc from having the carbs out.

Dan

[Nessism]

Dan,
Might be worth the experiment to move the needles up another notch; richens the mixture accross the range which usually doesn't hurt anything.

[salty_monk]

Hi Ed,

I'm already one up from stock on these needles, going another one would take me to the limit of the needle adjustment range.....

I might have a play with them, want to take it out for a longer run before I do anything, these are just initial findings.

Dan

[KEITH KRAUSE]

I think I read somewhere that you're sure the spark quality and timing are good.
If so, your backfire is a rich condition. The bike can't handle the combination of the richer jet needle setting/richer main when you roll it on. Opening it suddenly will always worsen the condition. Sometimes it's the main, but I'm thinking it's the needle in this case. (I assume the air filter is oiled correctly too.) A true backfire seems somewhat surprising considering the jetting changes aren't that extreme. I'd think a moderate bog would be more likely but if it's backfiring as you say...
I'm not sure if you ever told us what the factory setting should be for the jet needles. For that pipe and K&N filter, one position richer is usually too much. A 1/2 position is common for these mods and usually works. Since the e-clips are already one position lower (richer), place an approx' .022" jetting spacer directly on top the clip and you'll have the 1/2 position richer. You can of course warm up the bike fully and do a solid 1/3 to 1/2 throttle chop test to see how the plugs look to better decide what to do. I'm betting 1/2 position, which I've said all along, will be right. Re-test after the change.
I think a 7.5 main increase is right, but 5 may be all it wants too. As I said above, sometimes there's a combination of the two jetting circuits that cause a temporary overlap problem and you then need to separate the two by testing at specific throttle positions. I'm still guessing the needle is the problem though.
As for the slight decel' pop, sometimes it's best to accept a little because richening the pilot circuit may cause worse problems. I think 1 full additional turn out (from factory) is all the pilot circuit would want. I don't know if your 40 pilot is stock but the stock pilot jet should work for these minor mods. I think the stock air jet should also work but if you went up one size it may be fine.

[salty_monk]

Hi Keith,

Thanks mate. I know you suggested a half (don't worry I'm not ignoring you) just didn't have the right spacers at the time & it's no big deal to make that swap "on bike".

I'm going out for a much longer ride with Hap today & will be putting new gas in the tank, riding at some elevation etc etc.

Those were only Prelim findings on about a 5 mile stretch.

I'll report back more later

Dan

[salty_monk]

Well after a full days riding on new gas etc here's what I can report.....

Runs great on pilots, not bad WOT but I just feel it's holding back on me a bit (doesn't run like the scalded cat that it did at Bruce's when we removed the air filter with the old setup...)

When it's hot, as soon as I get into the needles it starts to backfire & this appears to go on until I get into WOT.

Hap thinks it might be lean after riding it, I'm not sure but I know my new pipes aren't going blue. It also "seems" to run better when it's been left to cool down for a while & then the backfire comes back which suggests rich I think.

I know KENT runs 120 mains on his 1100GL with the same setup as mine, maybe I do need to go back to 5 up rather than 7.5 up from the 115.

First thing I will do is try to restrict the filter with tape & go out for a good run, see what that does, see if it gets better, worse or no difference. If it's worse then I may try cleaning the K&N just to be double sure it's not that & bring the needles down a half notch but as WOT isn't where I think it should be either I think it probably does need a change in the main jets.

Anyway, at least we had a good days riding & it's getting there

[KEITH KRAUSE]

I would chop off and check the plugs after a 1/3 throttle run. Do what the plugs say to. If the backfire is carb related, I'm a little surprised that just 1 position richer would be the cause. I always have to see the plugs before deciding anything.
Are these Canadian needles the same as used in U.S. models, other than being adjustable of course?
Unless there's something different about those needles, there's only 3 possible positions that will work (factory/1/2 position richer/1 full position richer) for your minor mods, and you've already discovered 1 full position is apparently too rich. It should be easy to find the right one. I think the 1/2 position will work. If it still backfires at 1/2 position richer at 1/3 to 1/2 throttle, then you have some other problem. A 1/2 position richer shouldn't cause backfiring.
That pipe, in good condition, WILL flow better than a stock exhaust and should require at least 1 full size (5) richer but shouldn't require more than 2 full sizes (10). If the pipes packing is gone or nearly shot/compromised/incorrect packing/packed too tight, etc, this range and the pipes performance, can change. Again, not too hard to find the right main because your mods normally require a range of not less than 2.5 and not more than 10 richer. Stage 1 jet kits are within these ranges. Normally, with your minor mods, you wouldn't ASSUME the jetting is lean, you would first test the existing main (the 115?) and note performance and read the plugs, to be sure. Then I generally go the richest that makes sense, in this case, a 125 max. It still depends on exactly what the plugs/performance was with the 115's. If quite a bit white, then go for the max (125) and work your way back if the following performance/plug reads say to. If the 115 read was just somewhat lean, a 122.5 or 120 makes better sense.
More often than not, 5 to 10 works in your case. 7.5 would be the logical initial attempt if you're "trying to save time/money" and want the supposed best chance to get it right the first try. But all bikes can be different. There can be factors that are unknown.
Your complaint that the mains seem to be "holding it back a bit" could be from running rich or lean. Restricting the stock air box subjects the motor to poor flow conditions. I don't see how anyone get trustworthy results from this. Sure, you've cut down the air flow and think this absolutely exposes a suspected rich condition by "making it even richer" but you've also decreased the vacuum available to draw fuel through the jets, which in itself, is creating a lean condition. I know you're just trying to see if something gets worse or better but if anything, remove the airbox lid if you need help deciding what is rich or lean. I'm not much of a fan of "temporary" intake mods, either "richening" or "leaning" attempts. The bike will not be permanently run with these mods. Performance/plug checks and determining the right jetting should be done with the equipment on the bike as it's meant to be. Find the right jet by either increasing or decreasing the size according to performance/plug reads.
Testing with significant load on the motor (uphill, vs level or downhill) will more easily expose a lean condition. If lean, pinging may show up/be more noticable as the motor becomes hot.
A true rich condition generally worsens as the motor heats up.
At full operating temp, rev the motor (not into redline). Just as the throttle is full open and the rpm's quite high, have someone pass a taught white rag into the exhaust flow, a couple inches off the end is fine. Don't pass the rag as you first open the throttle as this will involve overlap from the pilot and needle circuits. You just want to see what the main is doing, so the timing of the rag passing into the exhaust flow is important. It must be done quickly of course as you don't want to redline either. The rag shouldn't show excessive black deposits or smell too strongly of gas. Strong gas smell or wet/damp black deposits shows unburned fuel. This test can HELP in determining if you're rich but because of other factors, it's not an absolute test. For example, if you haven't revved the bike in some time, even if it's running spot on, you could see some black deposits come out simply from accumulation/not being revved high recently. Like plug reads, people may see things differently when inspecting the exhaust pipe color or exhaust itself. Many manufacturers say to read the end of the pipe instead of the plugs.
If you're still not sure what to do, as I said before, use extremes to find the right jet. Test the stock main first. Then go to the max jet that makes any sense and go from there. The right jet will be within that range.

[salty_monk]

Thanks Keith, I will order up some 120's & some 125's & see what happens.

I'm really at a loss for doing plug chops out here as there is nowhere safe but I may go do some with Bill one day when he's off work.

On the 115's with the stock exhaust the same effect was evident with both CA needles & canadian needles so I believe they are the same. I guess they could be a slightly different profile. I also have some stock 1,100GL needles too but I haven't tried those & as I don't know what the difference in profile is I'll leave well alone.

Dan

[GS Farmer]

I'm running a 81 1000G, with a Mac 4-1, and a stock style K/N filter. Went 1 size bigger on the pilot, and am running a 125 main, and I believe I have 4 radio shack washers under the needles, that seemed like alot but thats where it runs good. I have a DJ kit, and was going to go with the stage 3 and pods, but it runs well and I'm going to leave it alone. Good luck!!

[Nessism]

I'm running a 81 1000G, with a Mac 4-1, and a stock style K/N filter. Went 1 size bigger on the pilot, and am running a 125 main, and I believe I have 4 radio shack washers under the needles, that seemed like alot but thats where it runs good. I have a DJ kit, and was going to go with the stage 3 and pods, but it runs well and I'm going to leave it alone. Good luck!!

Glad your bike is running well but a question: did you remove the spring under the needle when you installed the washers? The height of the needle on GS Mikuni carbs is typically determined by the height of the stack ABOVE the clip, not below, because the spring pushes the needle up. A shorter washer stack above the needle effectively raises the needle.

[salty_monk]

I'm running a 81 1000G, with a Mac 4-1, and a stock style K/N filter. Went 1 size bigger on the pilot, and am running a 125 main, and I believe I have 4 radio shack washers under the needles, that seemed like alot but thats where it runs good. I have a DJ kit, and was going to go with the stage 3 and pods, but it runs well and I'm going to leave it alone. Good luck!!

Coming to that conclusion that I need to go up some.
Played with the needle today with these 122.5 jets & basically making it leaner just aggravated the situation, runs best on either stock (3rd position) or with clip one down from there. (I tried all the settings, I can switch needles like an F1 race team now....)

I'm going to get some 125's & try it. I have some 130's but I think they will be way too much.

Can you confirm what you did with the needle as per nessism question?

I have some 42 pilots (one up I think) that I could put in there. What Air jets are in yours? Mine has 180's but the Canadian carb rack I have has 160's (along with the 42 pilots & 130 mains).

Cheers,

Dan

[salty_monk]

Well everyone likes feedback... Put the 125's in tonight & gave it a run, just a couple of miles. So far so good, much better. Try to give it a better run tomorrow.

The pilots are about 2.5 turns out Canadian needles (identical to stock apart from the grooves) are up one notch (E clip down one notch).

Pilot jets are the 40's, air jets are 180's.

Small stumble on idle (not whilst riding) so I think the pilots need fine tuning & maybe it needs another vac balance (I've changed jets, slides, exhaust etc since it was last done).

Dan

Dan