SM610 Jetting Question

[Highpower]

I was wondering if anyone can offer some insight to my jetting situation. Note that I’m a total amateur when it comes to jetting so I may be missing something obvious. My setup used to be this:



185 Main

JD Red Needle with the clip at pos. 5

45 Pilot

2 turns on the fuel screw (seems to run smoothest there)

Power Now and Power Now Plus intake attachments

Barrett Pipe

Opened the air box.



Everything else is basically stock. Ran OK with the above settings. Decent power, better than stock, but I wasn’t totally happy and wanted more out of it. So I tried experimenting and moved the clip on the Needle Jet to position 6 (richer I think). And the thing screams in the mid-range now. Lots of power and a totally different bike at 1/3to 3/4 throttle opening. But it seems like it has a sharp knee in the power band, where it actually has a little bit less power now down low and then comes on all the sudden when the revs pick up.



I tried increasing the size of the pilot back to a 50 and it ran terrible so I went back to 45. If I turn in the fuel screw it stutters a bit down low, so I don't think I should go smaller on the pilot.



Is there anyway I can get the best of both worlds and keep this awesome mid-range that I discovered and get my low end grunt back? Is there something I’m missing? Accelerator pump adjust maybe?



Any suggestions are appreciated.

[dukepilot]

Try a 180 main.

[jimi]

I put a Boysen Quickshot on mine just to try it out. Verdict is still out. Bike was running okay with:

180 main
45 pilot (I think that's what the JD kit comes with)
red needle, 5th
2-turns out
stock airbox lid
Leo Vince full

It just bogged when getting on it at anything under 4000. Pulled okay after that.

I put on the Quickshot, leaving everything else alone. Boysen says to turn the mixture screw out another 0.5 turns, but I wanted to try it without.

It pulls HARD from lower rpms. The off idle is instant power. Something not quite right though, so I try the 0.5 turns out. Runs worse, backfiring under decel, and surging at any steady throttle. I'm going to out here later, and try turning it in 0.25 and see if that helps.

Thanks to whoever suggested the Stealth Racing fuel screw. Very nice, and if I had to take the carb out one more time, I was going to throw the bike in a ditch.

I'd like to see if I can get the Quckshot sorted, as I like that instant feeling the throttle has now, but as of now, the bike ran better before.

[bill900]

I am at the same place you are, except Leo slip on vs the full system. Bike runs good, just hate the damn popping on decel......There has got to be a way to get that tuned out. Agree about the fuel screw and the quick shot. I found it better when i went 1/8th turn in from where I had it, or 1 and 1/8th turns out. Still some slight popping, but runs really good.

[Highpower]

Originally Posted by dukepilot

Try a 180 main.

Thanks dukepilot. I'll try that this weekend. Have to ask though - Will changing the main really affect the bottom end of the throttle range? I thought the main circuit only affected top end.

[Highpower]

Originally Posted by Highpower

Thanks dukepilot. I'll try that this weekend. Have to ask though - Will changing the main really affect the bottom end of the throttle range? I thought the main circuit only affected top end.

OK. Forget I asked.

I just swapped it out my 185 to a 180 and took a night ride. For the first time ever it can do 3rd gear power wheelies

Strange how such a small change can make such a difference. I would still like to know why changing the main jet got my low end power back. According to the JD charts it's not supposed to affect bottom end ... Jetting is black magic and dukepilot is the master wizard ...

Thanks man!! I owe you one!

[dukepilot]

Originally Posted by Highpower

OK. Forget I asked.

I just swapped it out my 185 to a 180 and took a night ride. For the first time ever it can do 3rd gear power wheelies

Strange how such a small change can make such a difference. I would still like to know why changing the main jet got my low end power back. According to the JD charts it's not supposed to affect bottom end ... Jetting is black magic and dukepilot is the master wizard ...

Thanks man!! I owe you one!

Glad it worked out for you. The carb circuits have an overlapping effect. By fattening up on the needle setting you made the off idle mixture a little richer. By going down to the 180 MJ, you leaned out the bottom just enough to retain the benefit of the mid range improvement you noted with the new needle setting. It is true that the main jet has the greatest effect at WOT but it will have a small effect at part throttle and idle. Jetting is trial and error, at least for me with a little deductive reasoning and guess work thrown in.

[buffallodan]

I thought raising the needle's clip you were lowering the needle and therefore leaning the mixture? I am a noob and trying to learn the basics please ...TIA

Dan

[bill900]

Raising the clip does lean it some as you are dropping the needle lower in the emulsion tube.

He said he moved to position 6, not raised or lowered. Typically when referring to the clip position on needles(that are adjustable), the position starts at the top of the needle and goes down. So when you say 5th position, it is the 5th slot from the top of the needle. Going from position #5 to #6 richens or going to #4 would lean.......

[dukepilot]

Originally Posted by buffallodan

I thought raising the needle's clip you were lowering the needle and therefore leaning the mixture? I am a noob and trying to learn the basics please ...TIA

Dan

You are correct. Some people refer to raising the needle to richen the mix or lowering the needle to lean it out. This is accomplished by lowering the clip to make it richer or raising the clip to lean the mix out.

[dukepilot]

Originally Posted by jimi

I put a Boysen Quickshot on mine just to try it out. Verdict is still out. Bike was running okay with:

180 main
45 pilot (I think that's what the JD kit comes with)
red needle, 5th
2-turns out
stock airbox lid
Leo Vince full

It just bogged when getting on it at anything under 4000. Pulled okay after that.

I put on the Quickshot, leaving everything else alone. Boysen says to turn the mixture screw out another 0.5 turns, but I wanted to try it without.

It pulls HARD from lower rpms. The off idle is instant power. Something not quite right though, so I try the 0.5 turns out. Runs worse, backfiring under decel, and surging at any steady throttle. I'm going to out here later, and try turning it in 0.25 and see if that helps.

Thanks to whoever suggested the Stealth Racing fuel screw. Very nice, and if I had to take the carb out one more time, I was going to throw the bike in a ditch.

I'd like to see if I can get the Quckshot sorted, as I like that instant feeling the throttle has now, but as of now, the bike ran better before.

If you haven't already done so, install a CR8EIX plug, set your fuel screw at 1.5 turns out as a starting point and try the next size smaller pilot. Also, does the bike run better or worse once the engine is at operating temp? If it is surging at steady throttle, it probably has nothing to do with the Boyesen plate. More likely your pilot and needle settings need a little tweaking. With your settings, I doubt that you are too lean on the needle, so try the next size smaller pilot first to see if that cleans it up. Once the bike is at operating temp, set the idle at 1800 rpms, slowly turn the fuel screw in till the idle speed drops, then back out slowly to the point where the idle speed picks up. Reset your idle speed to around 1600 rpms.

If the smaller pilot works out, just remember you may have to go back to the 45 when the temps cool off later in the year.

[jimi]

Thanks for the suggestions. I did get the CR8EIX plug, never could tell a difference with it though, but I've been making multiple changes at once, which I know is a bad thing.

Do you know what size if the next pilot down? Is there a 44 for example? I think I know a dealer that stocks individual jets.

Seems to run worse at operating temp, more backfiring. Also, I have to keep the idle high or it often stalls when stopped, so it's usually around 1800. I set it lower, but it creeps up. That makes me wonder if there is a leak somewhere.

I will try the fuel screw changes. I hadn't heard that method of setting it, but that's interesting.

I also have an appt in a few weeks with GP to have the bike serviced. Not so much because I can't do the service, but I want an expert to go over it, make sure it's running like it should, and run it on the dyno with EGA and see what it looks like. Hopefully I can get it close beforehand. I'll post the results.

Thanks again.

[zrxchris]

Why is it my shadetree-slip-on jetting is so close to what you guys are running in respect to needle position and main jet and yet it runs like crap with the JD pilot

this is what I ran for the first few months

185 main
JD red needle, 5th position
stock pilot
2 turns out on the fuel screw
boysen pump plate
my bike already had the leak jet put in I guess by Kirk's cycle, we pulled it out and matched excatly with the JD leak jet
iridium plug

I was surging some at around 5K rpm at cruising speed (1/4 throttle or less)
so I moved the clip to the 6th position and came out another 1/2 turn on the fuel screw and it pulls harder, comes up it 2nd with just slidin back on the seat some even with my fat ass in the seat, but now I notice after it is warmed up and ran for a 15 minutes or so it still surges a little bit but a about 4500rpm

I know I have some seasonal jetting issues as it almost 100 degrees down here in the south nowadays. So I know I kinda have to have summer and winter jetting changes.

I still don't get how when ya uncork the bike you go down in pilot size, seems like when ya deretrict the bike you would usually need a bigger pilot

My local jetting guru says if I open up the airbox I should get a 52 pilot to start of with

I tried the JD pilot and with a 180 and 185 main it just ran like crap......I know it tough b/c I don;t have a leo or arrow slip on, but if I am in the same ball park as you guys as far as main jet, needle and fuel screw....wouldn;t there be some rememdies I could look into.

dukepilot, any ideas ?

sorry for the shadetree slip-on thread jack

[Highpower]

Originally Posted by zrxchris

Why is it my shadetree-slip-on jetting is so close to what you guys are running in respect to needle position and main jet and yet it runs like crap with the JD pilot

this is what I ran for the first few months

185 main
JD red needle, 5th position
stock pilot
2 turns out on the fuel screw
boysen pump plate
my bike already had the leak jet put in I guess by Kirk's cycle, we pulled it out and matched excatly with the JD leak jet
iridium plug

I was surging some at around 5K rpm at cruising speed (1/4 throttle or less)
so I moved the clip to the 6th position and came out another 1/2 turn on the fuel screw and it pulls harder, comes up it 2nd with just slidin back on the seat some even with my fat ass in the seat, but now I notice after it is warmed up and ran for a 15 minutes or so it still surges a little bit but a about 4500rpm

I know I have some seasonal jetting issues as it almost 100 degrees down here in the south nowadays. So I know I kinda have to have summer and winter jetting changes.

I still don't get how when ya uncork the bike you go down in pilot size, seems like when ya deretrict the bike you would usually need a bigger pilot

My local jetting guru says if I open up the airbox I should get a 52 pilot to start of with

I tried the JD pilot and with a 180 and 185 main it just ran like crap......I know it tough b/c I don;t have a leo or arrow slip on, but if I am in the same ball park as you guys as far as main jet, needle and fuel screw....wouldn;t there be some rememdies I could look into.

dukepilot, any ideas ?

sorry for the shadetree slip-on thread jack

Looks like we are in the same boat. Since it jacked up to 100 degrees here my 6th position needle setting isn't working as good as it used too. I too get surging at 4500rpm, and sometimes (if it's really hot) some hesitation off of closed throttle. I think I may go back to a 5 clip position until it cools off a bit. Also thinking of putting in the leak jet that came with my JD kit.

Aren't carburetors fun?

[jimi]

Fed up with pulling the carb yet again, I took it to GP to let them mess with it. Their conclusion after Paul spent some time with it, was to go down to a 40 pilot. It was just running too rich most of the time. Yeah, the hot weather probably wasn't helping it.

Bike still has that midrange stumble though. They tried a couple of different ECUs, and had the same result. Not really sure why, seems some bikes are more prone to doing it.

[nmilne]

So the word on the mid-rpm misfire seems to be to disconnect the tps ... I've done plug, pipe and jetting and it still misfires exactly the same as stock, which leads me to think that maybe it is the tps. I feel bad about disconnecting the thing though as they're generally put there for a reason, unless its just an emissions related thing to try and retard ignition advance during the rpm period they normally do the emissions testing at?

Anyhoo, worth a go, might try it this weekend

[dukepilot]

In stock form, the 610 is a bit lean on the needle and too rich on the pilot. The JD red needle has a slighty thinner taper creating a richer mix off the bottom through the mid, which allows you to run a smaller than stock pilot. With the hot temps at sea level, you may very well need to go down to a 42 or 40 pilot. I'm going to give it a try myself this weekend.

[jimi]

Bike seems to run better with the 40 pilot for now. I think I need mess with the fuel screw a little, but it is better.

I also bought a 42-tooth sprocket to put on, as my chain seems too tight to put the 16 on the front. I think that will make the freeway trips a little easier. Dont' know when I'll get that on though...

[Highpower]

Originally Posted by nmilne

So the word on the mid-rpm misfire seems to be to disconnect the tps ...

Yup. Unplugged mine. It's the only thing that worked. And with the jetting I'm running now it runs absolutely horrible with the TPS working. Runs awesome without it.

The default ignition map (TPS unplugged) goes to a rich setting it seems. So once you open everything up, the TPS map runs way too retarded an the thing runs like shit. So unplugging it is your best bet. So if you add a pipe, open up the airbox, and re-jet, it is probably a good idea to unplug the TPS.

BTW - I have toyed with the idea of adding a bias resistor on the wire coming from the potentiometer on the TPS. This would advance the timing to make it work for the increased air/fuel that my current mods are giving it. Just a theory so comments are welcome ...

[nmilne]

Yep, you're dead on ... I just disconnected it today and went for a short ride and can confirm that most of the miss has gone ... still the occasional one, though maybe the bike was just a bit cold, but a huge difference for sure