Diff spark plugs in each cylinder? (heat ranges) ect??

[RatyXS]

Ok so long story short. Picked a project up off a guy. Needed to be wired, jetted, finished, ect. I feel my jetting is close( def closer then orig) but the same in both carbs.. I cut my exhaust pipes up and re did them and the right pipe is a bit longer then the left. Right cylinder is considerably richer, plug shows this aswell as soot in the pipe. People have ran diff plugs in diff cylinders on cars due to intakes providing more air/fuel ect to a given cylinder, same as making fuel injected cars run a injector fatter then the other.. I am thinking rather then running diff jetting in my carbs, to up the heat range in the cylinder that is running richer. This is a fine way to do it in my opinion. I realize it doesnt mean a hotter plug(spark), but it works better in a given range. Maybe it is just me. Just curious if any one has went down that path. Thoughts ect. I plan to swap one out tom.

 

[xskid]

It makes sense to me, but who am I?

Posted via Mobile

 

[RatyXS]

^^^ makes total sense to me too LOL. It has been done many times in engines and diff exhaust set ups. Just wanting to get some ops from the XS fellas.

 

[ippytattoo]

Before changing spark plugs around it may be a good idea to make sure your float heights are the same and in spec as this could cause the 2 cylinders to be getting different air/fuel mixtures.

 

[plane_ben]

In my experience with twin carbed XSs, the left cylinder runs cooler. Thus having the darker plug. If your right plug is the darker one, and it typically is the hotter cylinder, I'd say you have a carb problem to find. Could be as simple as using a jet gage to make sure your jets are actually the same size. I've run into incorrect sizing issues before. Also, as said above, check your float level.

 

[RatyXS]

Float levels have been checked, were fine, but I still fine tuned them. Both carbs have been checked over and jetting is the same. It is weird. The plug that is the sootiest also have the steel bands a slightly blueish color( which would indicate lean) However the plug states other wise as well as the soot in the exhaust pipe. I will get to the bottom of this LOL, I am gona check it after it is hot with a heat gun. Just seems odd to me.

 

[RatyXS]

This is after about a 15 min right. left plug left cyl, vis-versa This is running this jetting

22.5 pilots, the recommended needles( still the fatter needle jets) clip on the leanest setting, both af screws 3/4. Bowls 24 mm. still seems rich?? And the temp today is 50-52 @ about 2-30 ft sea level. Thoughts?

 

[5twins]

It won't run right until you change the needle jets.

 

[ippytattoo]

Have you done the dead cylinder method of setting the A/F mixture? May need to start at the beginning and set valve lash and work your way through sync and A/F mixture to get it dialed in. I have never had that much show up after a 15min ride.

 

[RatyXS]

It won't run right until you change the needle jets.

This is absolute 100% needed ? I am going to switch carbs from one side to the other and see if it changes. The left cylinder runs fine, doesn't drop or lose fire. Guess I will have to do the NJ's but still seems as if both should be running the same as they are jetted the same. Hmmm this bike so far has been the most finicky bike I have ever dealt with EVER, lol

 

[RatyXS]

Have you done the dead cylinder method of setting the A/F mixture? May need to start at the beginning and set valve lash and work your way through sync and A/F mixture to get it dialed in. I have never had that much show up after a 15min ride.

These weren't totally fresh plugs, just cleaned up. All the valves, cam chain, timing is right, went over all of it. I know the MJ's are a little fat but that is something that can be taking care of that is not being the pita now LOL. No real stumble on a hard throttle roll or all the way up.

 

[5twins]

What needle jets are in there now? If it's the "Q" series that comes stock in the off-the-shelf two stroke versions of these carbs, they're too rich. You need something from the leaner "P" series, like a P-5 or a P-6. Fool with the mix screws and sync all you like, you won't get anywhere. The overly rich midrange is what's coloring the plugs so quickly.

 

[RatyXS]

Ok I see what your saying, butvI can grab a hand full of throttle and can pull this front tire in the air, I have zero hesitation from part throttle even with a hard snap of it under load, idle. My main issue is the idle. It will idle fine then put a cylinder out, give it some gas and it will come back. Yes I am running the needle jets that came with it so it is the Q, agree that is stil a rich area. However, I have asked before and has been said will the NJ play that much of a role at a stone idle ? I am not trying to be rude, but I have never ever seen it before like this. F it I guess if I swap carbs and it changes to the left cylinder it is a carb. I need to hunt down the p-5-6 NJ I guess, but still seems too strange. Also my riding is more of a 20-30 min short spurts from here to there, bar hopping type thing, not over the road.

 

[RatyXS]

So will a P-5 159 or 165 series work ? Also what is a 159 ''06'' NJ ? Thanks

 

[5twins]

You want the 159 series. Needle jets get richer as the letter of the alphabet goes higher, also the number after that letter. There are 5 or 6 number sizes with each letter size, for example P-0, P-2, P-4, etc. Once you get up to 8 or 9, the letter changes. In this case, after a P-8 or P-9 would come a Q-0 or Q-2. An O-6 would be leaner than the "P" jets since "O" comes before "P" in the alphabet. And they don't make every number, usually they go up in 2's. The exception is the "5". You will find a #5 size for many of the letters, probably because that's the halfway point in the letter's size range.

 

[DozerDan]

I think you are WAY over analyzing it.

 

[xskid]

So i take it was the needle jet sizing?

Posted via Mobile

 

[RatyXS]

You want the 159 series. Needle jets get richer as the letter of the alphabet goes higher, also the number after that letter. There are 5 or 6 number sizes with each letter size, for example P-0, P-2, P-4, etc. Once you get up to 8 or 9, the letter changes. In this case, after a P-8 or P-9 would come a Q-0 or Q-2. An O-6 would be leaner than the "P" jets since "O" comes before "P" in the alphabet. And they don't make every number, usually they go up in 2's. The exception is the "5". You will find a #5 size for many of the letters, probably because that's the halfway point in the letter's size range.

Thanks man.. Excellent. I figured if it was like jets the ( series means a diff style) but wanted to verify if that was the case, was not sure what in the hell the letters meant other then hearing the P was leaner then the Q. So that P-159 ( 06) jet would be the richer end of the P series jet then. Learn something new today means it wasn't a total waste.

I also thermo'd the cylinders with the bike running and the right cylinder is in fact running 20-30 deg colder then the left. So from what people have said that is backwards then normal, would the re=phase have any bearing on that? I am def going to switch to a hotter plug( AL 63) in both jugs, these plugs are black. hopefully it is dialed in the way I like it after that other wise I am burning this thing.

I think you are WAY over analyzing it.

Not at all lol. As I said in a earlier post, these bikes are WAY more finicky then anything I have ever fooled with, have done a fair share of bikes. Prob due to the dual carbs, 2 cylinders vs dual cylinders and 1 carb. This was just a headache from the get. Not running, some one else project that was totally un finished.

So i take it was the needle jet sizing?

I will know once the NJ's get here. I sure as hell hope it is, because then the bike will have the recommended jetting in it per the entire XS world hahaha.

Posted via Mobile

 

[xskid]

Well good luck man i hope u get it straighten out.

Posted via Mobile

 

[5twins]

Here's a page that will explain the Mikuni needle jet sizing a little bit more. It's actually mostly info taken from the Mikuni Tuning guide. You really should have that little booklet if you want to understand tuning these VMs .....

http://www.pjmotorsports.com/mikuni-needle-jets.html

Here's the tuning guide .....

http://www.mikuni.com/pdf/vmmanual.pdf