Boggy midrange - needle questions

[jeffasaurus2]

best of luck!

[MOC]

I fixed the petcock today and then reset the floats from 26 to about 24.5. Didn't get a chance to do any chops before dark but I took it for a spin and it pulls MUCH harder through the midrange. I'm going to need to fiddle with the idle mix a bit but it's much better. I'm not freaking about it burning up from lean condition as much anyway. Thanks fellas

[pete]

Hey mate, sorry I've been away on holidays and didn't see this or your PM until now.

My 450 has K&N pods and a quality custom 2 into 1 pipe that is very free flowing.

I'm still working out my tuning slowly and haven't done any plug chops yet to confirm, but so far this is what I have:

Float height is stock (26.6mm - the Clymer is wrong for these).
Stock pilots, still getting mixture screws set right.
Stock needles raised as high (rich) as they will go.
132.5 main jets but about to try 137.5 mains tomorrow.

Essentially from the rebuild my bike felt "boggy" just off idle up until about 1/4 to 1/2 throttle and had what I thought was surging when holding steady around the 1/4 throttle mark and I thought I had jetted it too rich.

When I finally started trying things, I discovered the opposite and that I had been running lean, so I had hesitation at part throttle and the surging was actually stumbling.

I probably need to go for a richer needle, but the length of the stock needles (4C3) is 48.3mm whereas all the Mikuni replacements I can get are just over 50mm, so doing a comparison to determine an appropriate needle will be a little difficult. I have measured the various diameters to make a comparison though.

I'm still slightly too rich on my mixture screws as I occasionally still get pops on decel and it has been improving as I lean them out.

It sounds like you're on the right track with richening things up, but with your needle, you will definitely be able to add more shims.

The way to add the shims is between the washer (8) and the C clip (7):



This is not the greatest photo in the world but you can just make out the shim here that I was trying:



I have also gone one step further in increasing throttle responsiveness and have trimmed just under 20mm from the slide springs as well, but don't do this unless you're really keen and have got them running right first...





You can also drill out the vacuum hole in the slide to get even more response but I haven't gone down that path yet, that's a little more drastic...

[MOC]

Pete, this is awesome. i'm glad you can identify with my trials and tribulations...

Regarding the shims. the problem i face is this:

Adding a washer beneath the clip won't raise the needle any more than it is already because it's already pushed firm against the base of the jet needle stem. (4) it took me about 3 teardowns with different washers to realize this. Raising the needles has meant removing the spacer (5) so that the needle can travel farther up towards the stem, but i've already pulled that spacer out. in other words, i'm at a dead end. The needle is pressed up against the stem as high as it will go and i've got nothing i can remove to free up its travel any further.

one of the consequences of raising the floats has been an idle mix that's too rich, so i've been trying to iron that out which i can't really sort out until i've got my midrange mix dialed in.

i think i could probably also use a bit more fuel in the 1/4 to 1/2 range, but again, i've run out of options in that department which is why i've resorted to gaming the floats


this leaves me with two options:

1 - play musical needles (nightmare scenario)
2 - risk modifying the needle stem (also a nightmare, and one i can't undo)

i'm hoping i can game the floats a bit more and be on target. the 130 main has proved to be enough at full throttle, although i haven't done any chops to confirm the mix is perfect. it pulls like a brute at WOT, so it's definitely not starving for fuel. it's just a tad bit lean from 1/4 - 1/2, which sucks because thats the band i'm in the most when i ride around baltimore.

fiddling will continue. I'll let you all know what i learn, and hopefully you might be able to figure yours out as well Pete.

cheers

[pete]

Wow ok, you really are quite a lot richer than stock!

One thing I'll add though is the US needles and mains are different to the Aus needles and mains. The stock needle for you guys is a 4C2 whereas in Aus it's a 4C3 and this is a slightly richer needle. The stock mains in the US are 115's whereas in Aus they're 117.5's, again slightly richer.

At this point if I were you I would try one of two things... see if you can get a hold of the Euro version Dynojet E3305 stage 3 kit or start playing with richer needles.

This page may help you somewhat with your needle selection:

http://www.mikunioz.com/needles_numerical_list.htm

I've measure my 4C3 needles but that won't help you with the 4C2, you will need to measure and compare.

You will see the stock needles are shorter than the genuine Mikuni replacements also to make it that much more difficult:



After a good ride in the sun (finally) yesterday, I reckon my needles are pretty good now but I think I still need bigger mains. Next size to try will be 142.5.

[MOC]

hmmmmmm interesting. any clues as to why they don't carry this dynojet kit stateside? i've found the 83+ model 450L kit on the dynojet website, but the fella on the phone said it wasn't compatible with my carbs. i'm skeptical, but not about to risk a bunch of scratch on something like that.

[pete]

I'm not sure, but I suspect emissions related.

For me to buy it here the local reseller wants $AU180+ for it which is why I just went with trial and error and Mikuni jets. I've spent less than $70 so far so I should be ahead even buying some more mains and needles.

The '83 and onwards are definitely not compatible with your carbs either, different floats, jets, and needle.

[Snyder450L]

My 2 Cents

I have an 82 GS450L that I have cut the mufflers off and replaced the air box with two individual pods. The stock needle is a 4c2, main jet is a 115 and the pilot is a 17.5. While riding from idle to 1/4 throttle the bike would accelerate but from 1/4-3/4 throttle it would bog down. At full throttle it would accelerate again. Also when decelerating it would back fire and spit and sputter.

I went to a local motorcycle salvage yard and purchased (2) 22.5 Pilot Jets and installed them. This cured the stumble from idle to 3/4 throttle by allowing more gas flow through the system. It also fixed the backfiring.

Now the only problem is at full throttle it spits and sputters from not getting enough full. If you turn the choke on all the way it smooths out at full throttle due to the choke reducing the amount of air being taken in.

Also when relieving the throttle from full throttle to idle the engine would hiccup and the return itself to idle, this resulting from the pilot jet attempting to produce enough full where the main is lacking.

Then next step for me is 130 main jets. I will keep you guys posted on my results after Tuesday when they come in at the local store as the salvage yard did not have these.

Also for elevation questions if there are any I live in the armenia mtn are of PA.

[Snyder450L]

I have an 82 GS450L that I have cut the mufflers off and replaced the air box with two individual pods. The stock needle is a 4c2, main jet is a 115 and the pilot is a 17.5. While riding from idle to 1/4 throttle the bike would accelerate but from 1/4-3/4 throttle it would bog down. At full throttle it would accelerate again. Also when decelerating it would back fire and spit and sputter.

I went to a local motorcycle salvage yard and purchased (2) 22.5 Pilot Jets and installed them. This cured the stumble from idle to 3/4 throttle by allowing more gas flow through the system. It also fixed the backfiring.

Now the only problem is at full throttle it spits and sputters from not getting enough full. If you turn the choke on all the way it smooths out at full throttle due to the choke reducing the amount of air being taken in.

Also when relieving the throttle from full throttle to idle the engine would hiccup and the return itself to idle, this resulting from the pilot jet attempting to produce enough full where the main is lacking.

Then next step for me is 130 main jets. I will keep you guys posted on my results after Tuesday when they come in at the local store as the salvage yard did not have these.

Also for elevation questions if there are any I live in the armenia mtn are of PA.

Ok I have received the 130 main jets and installed them. Now the bike runs very strong after I adjusted the air/ fuel screws to compensate the change in the mixture. Now I will ride it a couple tanks and then check the plugs to see if im running to rich or lean now. I will keep on posting results as they come.