Carb Tuning Success Story

[motoman]

Understand your frustrations getting that scoot runnin' correctly, but we here have to make judgement calls not actually being there with the bike, and sometimes don't get the whole story when an issue arises. Several of us here have decades of experience with these and other bikes and ****-loads of experience in the automotive world whether it be everyday drivers or full on race motors. That doesn't even count the many that are electrical experts, professional painters etc.........think you get the picture. We here have never failed yet to help someone bring these bike to not only life, but running perfectly. Sometimes it takes a bit longer than if we were actually there, but never have seen a failure yet. Lack of info sometimes and the one asking questions sometimes tend to think they are asking dumb questions, so aviod giving details as to what they have or not have done to the point of asking. Not the case here, as the only dumb question was the one NOT asked. I, as many others have followed the issues with this scoot, so don't underestimate when we ask specific details that YOU may not think are relavent. No offense intended, but some of us here are decades and many steps ahead of you when we ask something that you may think is non-relavent. Ask away, and do try to follow what we suggest. We like to see all have success AND fun while doing it. The permanent grin WILL be worth the effort......ONE step and ONE change at a time till you and the scoot are happy.

[IanDMacDonald]

Thanks Brant, I appreciate it. I will have to re-fuel and reset the odometer as somehow I forgot to, and I'm at over 200+ miles, and I still have a half tank of gas. no way is my tune that well. After I get a definitive mpg, I'll pull my carbs and verify float height and pilot/main jet size. I'll probs do that next week when I run her out of gas.

[motoman]

Thanks Brant, I appreciate it. I will have to re-fuel and reset the odometer as somehow I forgot to, and I'm at over 200+ miles, and I still have a half tank of gas. no way is my tune that well. After I get a definitive mpg, I'll pull my carbs and verify float height and pilot/main jet size. I'll probs do that next week when I run her out of gas.

....welcome, meanwhile keep an occassional eye on the plugs, specially the two inner cyl. A little black is ALWAYS better than a hint of grey, aluminum on the plug is NEVER a good thing.

[DGXSER]

You guys underestimate me, lol. I put brand new plugs in after I got my final tune. I did not have my tan coat on the plugs yet after running it down to work and back the day before yesterday. So, after I got home, I turned the plugs a quarter turn (having a box fan on the engine, letting it idle), and the plugs instantly carboned. I cleaned the plugs with contact cleaner, turned the screws back to where they were, and that's where I am now. If I do a slow roll on the throttle, I have no hesitation, and the bike screams through all gears. But, if I WOT in-gear right now, I have a slight stumble. Runs great otherwise all the way up to redline.

I noticed nobody commented on my statement regarding the pilot jets, and my lack of needing to switch them.

Ian, no one is under or over estimating your abilities or knowledge, simply giving you information to hopefully resolve your problems.

As to your jetting, yes, I agree, if the bike ran fine before you changed the timing components with the jets you have, then it is most likely going to run just fine with those jets now. What were the mixture screw settings when it ran "like a raped ape in a cage"? Whatever those settings were, start from there. That should give you a very good starting point.

For those that might not have caught this, Moto's concern about mercury does not apply to the Mogan Carbtune tool alot of folks are using, those are not mercury filled tubes. You can hammer the throttle all you want while running.

The change in timing is going to effect how the bike runs, it may be the source of the change in performance your experiencing. No carb tuning will rectify the change from the timing adjustment.

Do clean your plugs or use new after each change in tuning. Looking at the color of the plugs after you let it idle for about 5-10 minutes will give you a good idea of how well the mixture screws are set. When I have a concern with low end performance, I ride the last 2-3 miles to my house (which is all 35 MPH zones) in 5th gear, keeping the RPMs close as I can to 2k or less. Then check plug color. This gives me the low end under load look at the plugs color.

[IanDMacDonald]

Thanks for confirming my suspicions Doug. With regard to those "settings", they are now unknown to me, as I stupidly reset to 2 1/2 turns, automatically assuming a too rich/lean condition upon installing the de-tuned advance. I apologize if I offended anyone. I guess I get a little cocky sometimes, and I have no grounds for that (especially with "ruining" the bike, lol).

I feel I am at a good point in my tune right now, where only a quarter turn is the difference between a carboned plug and not. It's not right, and I'll work on to see what tje trick is.

[DiverRay]

Ian, Have you re-synced the carbs since the "last" adjustment? Just asking, as slightly out of sync WILL cause a stumble, BTDT. IF you are going to pull the carbs, you WILL need to re-sync once again. It's a pain, but it's also the ONLY way to get it running properly. And no, a color tune is NOT a sync, mercury/vacuum gauges, or the Morgan tune is what you need to sync carbs.

[IanDMacDonald]

Yup, carbs synced spot-on with Carb tune.

[motoman]

Ian, no one is under or over estimating your abilities or knowledge, simply giving you information to hopefully resolve your problems.

As to your jetting, yes, I agree, if the bike ran fine before you changed the timing components with the jets you have, then it is most likely going to run just fine with those jets now. What were the mixture screw settings when it ran "like a raped ape in a cage"? Whatever those settings were, start from there. That should give you a very good starting point.

For those that might not have caught this, Moto's concern about mercury does not apply to the Mogan Carbtune tool alot of folks are using, those are not mercury filled tubes. You can hammer the throttle all you want while running.

The change in timing is going to effect how the bike runs, it may be the source of the change in performance your experiencing. No carb tuning will rectify the change from the timing adjustment.

Do clean your plugs or use new after each change in tuning. Looking at the color of the plugs after you let it idle for about 5-10 minutes will give you a good idea of how well the mixture screws are set. When I have a concern with low end performance, I ride the last 2-3 miles to my house (which is all 35 MPH zones) in 5th gear, keeping the RPMs close as I can to 2k or less. Then check plug color. This gives me the low end under load look at the plugs color.

DGXSER, your catagory explanations are spot on, and simple to understand.........hell, thinkin' I'll just let you throw the answers out there.....

[IanDMacDonald]

Not So Successful

The SYMPTOMS: Requires light throttle upon start-up, STILL poor gas mileage, when the choke is all the way out, the idle does not rise to 3k like it did before, and now sometimes when the bike is warm, and I come upto a stoplight, the idle drops below 1k and the bike stalls out. I checked for vacuum leaks, etc. Don't know if it's related, but I let the bike idle too long at half-choke the other night, I pushed-in the choke and the bike died. I let it cool down, and it ran fine after.

[motoman]

The SYMPTOMS: Requires light throttle upon start-up, STILL poor gas mileage, when the choke is all the way out, the idle does not rise to 3k like it did before, and now sometimes when the bike is warm, and I come upto a stoplight, the idle drops below 1k and the bike stalls out. I checked for vacuum leaks, etc. Don't know if it's related, but I let the bike idle too long at half-choke the other night, I pushed-in the choke and the bike died. I let it cool down, and it ran fine after.

A bit to low fuel levels in bowls will cause both those symptoms. Know it's a bit of a pain, but may wanna double check the millimeter setting of all eight of those just to be sure to eliminate that as an issue. JAT.

[IanDMacDonald]

Yeah, I guess I'll pull them off tomorrow and check float level, alone with pilot/main numbers, etc. Thank you for the thought.

[motoman]

Yeah, I guess I'll pull them off tomorrow and check float level, alone with pilot/main numbers, etc. Thank you for the thought.

A-ha.......again the plot thickens..............besides numbers.......Genuine Mikuni swirly logo, or numbers mean nothing and useless, unless you intend to chase your tail......just sayin'......

[IanDMacDonald]

Checked everything over tonight. All genuine Mikuni jets. The Pilots were 42.5, however, the Mains were 140. I wonder if I dropped down to stock 137.5, some of those stumbles would be eliminated? Yet, I do have a less than stock airbox with Mac 4-2's. Float height was spot-on @ 25.7 mm.

[motoman]

Checked everything over tonight. All genuine Mikuni jets. The Pilots were 42.5, however, the Mains were 140. I wonder if I dropped down to stock 137.5, some of those stumbles would be eliminated? Yet, I do have a less than stock airbox with Mac 4-2's. Float height was spot-on @ 25.7 mm.

That one step rich with the mains could be questionable. The Mac's may or may not cause an issue, but IMO, that would be at the upper-upper rpm range. Same goes for 'slightly modified air box', whatever that may mean. I'd start with the 137.5's that are stock as a baseline, set mixtures and sync. See if it pulls hard and quick all the way to redline with no slowing of rpm gain towards that upper end for correct mains. Rollin' in third at around 3K, twist it and watch that tach goes quicly at same rate all the way up to and even a bit past the 8500rpm range. Should climb excepionally quick from 6-8.5K if mains are correct.

[IanDMacDonald]

Yuppers, I'll get to the shop in the morning before work. I was waiting on your reply Motoman. Thank you. Will try the 137.5's tomorrow after work.