Those Hoodoo carb Voodoo....

lotusmark · Post by **lotusmark** » Fri May 01, 2009 4:35 pm

I've installed the Unifilter and a 105 Main jet. The scooter stumbles when cruising at about 20mph and applying WOT. I have not messed with the mixture yet. Smaller jet, larger jet, or mess with the mixture?

Lostmycage · Post by **Lostmycage** » Fri May 01, 2009 4:44 pm

What's your spark plug say?

Do you have a free-flowing exhaust (Prima)?
How did you install it - on the intake tube or on the carb?
What did you do with the engine vent tubing?

JettaKnight · Post by **JettaKnight** » Fri May 01, 2009 4:46 pm

lotusmark wrote:I've installed the Unifilter and a 105 Main jet. The scooter stumbles when cruising at about 20mph and applying WOT. I have not messed with the mixture yet. Smaller jet, larger jet, or mess with the mixture?

The same thing happened to me when I had too large of a jet installed.

lotusmark · Post by **lotusmark** » Fri May 01, 2009 4:49 pm

Lostmycage wrote:What's your spark plug say?

Do you have a free-flowing exhaust (Prima)?
How did you install it - on the intake tube or on the carb?
What did you do with the engine vent tubing?

Prima with the Uni on the end of the intake tube. Engine venting is in the stock position. Haven't pulled the plug yet. Do I run at WOT and turn the bike off to get an accurate reading?

ScooterTrash · Post by **ScooterTrash** » Fri May 01, 2009 4:57 pm

lotusmark wrote:
Lostmycage wrote:What's your spark plug say?

Do you have a free-flowing exhaust (Prima)?
How did you install it - on the intake tube or on the carb?
What did you do with the engine vent tubing?

Prima with the Uni on the end of the intake tube. Engine venting is in the stock position. Haven't pulled the plug yet. Do I run at WOT and turn the bike off to get an accurate reading?

honestly if you don't know how you shouldn't be messing with it, I know what i'm doing and i'm having trouble's tuning the buddy.

105 is too small btw, it's stumbling cause it's lean

lotusmark · Post by **lotusmark** » Fri May 01, 2009 5:03 pm

honestly if you don't know how you shouldn't be messing with it, I know what i'm doing and i'm having trouble's tuning the buddy.

105 is too small btw, it's stumbling cause it's lean[/quote]

I like to learn by doing.

djelliott · Post by **djelliott** » Fri May 01, 2009 5:04 pm

ScooterTrash wrote:
lotusmark wrote:
Lostmycage wrote:What's your spark plug say?

Do you have a free-flowing exhaust (Prima)?
How did you install it - on the intake tube or on the carb?
What did you do with the engine vent tubing?

Prima with the Uni on the end of the intake tube. Engine venting is in the stock position. Haven't pulled the plug yet. Do I run at WOT and turn the bike off to get an accurate reading?
honestly if you don't know how you shouldn't be messing with it, I know what i'm doing and i'm having trouble's tuning the buddy.

105 is too small btw, it's stumbling cause it's lean

Mine fell on it's face until I got up to a 115. Had a 120 for awhile but the top end was to rich.

lotusmark · Post by **lotusmark** » Fri May 01, 2009 5:06 pm

Mine fell on it's face until I got up to a 115. Had a 120 for awhile but the top end was to rich.[/quote]

I didn't want to jet up too quickly. I have 105 thru 120. I'll try the 115.

Lostmycage · Post by **Lostmycage** » Fri May 01, 2009 5:23 pm

Chances are you're going to have to go to about a 110 and then you're *probably* going to need to bump the needle up.

Running too lean will burn up your piston, running too rich will foul a plug. The plug's a lot easier to replace. Start on the rich side.

Is your Prima turning a nice rainbowish shade of blue yet?

djelliott · Post by **djelliott** » Fri May 01, 2009 5:25 pm

Lostmycage wrote:Chances are you're going to have to go to about a 110 and then you're *probably* going to need to bump the needle up.

Running too lean will burn up your piston, running too rich will foul a plug. The plug's a lot easier to replace. Start on the rich side.

Is your Prima turning a nice rainbowish shade of blue yet?

True that. I had to bump the needle up one as well.

lotusmark · Post by **lotusmark** » Fri May 01, 2009 7:25 pm

I'm familiar with Webers, Dellorto's, Mikuni's and Keihins, but since there is no slide, how do you get at the needle?

djelliott · Post by **djelliott** » Fri May 01, 2009 7:29 pm

lotusmark wrote:I'm familiar with Webers, Dellorto's, Mikuni's and Keihins, but since there is no slide, how do you get at the needle?

You have to shim it up with a very small washer. I had to fabricate one. It's about 5mm in diameter with about a 4mm hole and 1mm thick. That's where I started and so far she seems OK.

Lostmycage · Post by **Lostmycage** » Fri May 01, 2009 7:33 pm

The plastic cap on the top of the carb houses the diaphragm needle and spring. Careful with the diaphragm, it's really thin. Also, once you undo the two screws, the spring will want to launch the plastic top off the top. Mind the spring base lines up in the shaft when you're reassembling.

lotusmark · Post by **lotusmark** » Fri May 01, 2009 7:49 pm

So you have to physically turn the carb upside down to get it to drop out?

djelliott · Post by **djelliott** » Fri May 01, 2009 7:53 pm

Lostmycage wrote:The plastic cap on the top of the carb houses the diaphragm needle and spring. Careful with the diaphragm, it's really thin. Also, once you undo the two screws, the spring will want to launch the plastic top off the top. Mind the spring base lines up in the shaft when you're reassembling.

BWAHAHAHAHAHAHAHA!

I totally did it wrong then. I shimmed it up from the other side. Well at least that solves the mystery of where my top end went. Funny how the midrange still smoothed out. I'll have to fix that tonight.

I shimmed the jet itself which now makes a whole lot of sense because instead of moving just the needle the whole guide and everything is up by a millimeter. Total voodoo fail on my part.

lotusmark · Post by **lotusmark** » Fri May 01, 2009 7:59 pm

So... is there a c clip on the needle like Keihins or Mikuni's?

djelliott · Post by **djelliott** » Fri May 01, 2009 8:01 pm

lotusmark wrote:So... is there a c clip on the needle like Keihins or Mikuni's?

I'll tell you tonight after I do mine properly. If not just use small washers.

lotusmark · Post by **lotusmark** » Fri May 01, 2009 8:24 pm

In polite response to Scootertrash. I'm no stranger to wrenching. My current Lotus has been modded to 225hp from a 1.8 NA. It weighs 1450 lbs without my fat arse in it and on the track will outhandle cars with twice the HP, just not in a straight line!

Lostmycage · Post by **Lostmycage** » Fri May 01, 2009 8:31 pm

It looks more like a nail. I'll try and snap a shot of it... good grief my list of things to do is getting longer and longer.....

Here's what the needle looks like (not the same as ours, but it gives you an idea of why a washer (Radio Shack PN: 64-3022 - 100 pack assorted washers - $2) has to make due instead of a clip (no clip slots).

djelliott · Post by **djelliott** » Fri May 01, 2009 8:52 pm

lotusmark wrote:In polite response to Scootertrash. I'm no stranger to wrenching. My current Lotus has been modded to 225hp from a 1.8 NA. It weighs 1450 lbs without my fat arse in it and on the track will outhandle cars with twice the HP, just not in a straight line!

Nice! That's got to fun on the track.

Kaos · Post by **Kaos** » Fri May 01, 2009 9:13 pm

Just to get in on the fun, yes your jet is way too small. I'm running a 100 with the stock airbox right now, and I'M running too lean, so you're likely dangerously too lean. Like others said, Read your plug.

djelliott · Post by **djelliott** » Fri May 01, 2009 9:18 pm

Lostmycage wrote:It looks more like a nail. I'll try and snap a shot of it... good grief my list of things to do is getting longer and longer.....

Here's what the needle looks like (not the same as ours, but it gives you an idea of why a washer (Radio Shack PN: 64-3022 - 100 pack assorted washers - $2) has to make due instead of a clip (no clip slots).

Nicely done pal. I feel like a tool for getting it wrong. What I did seemed to make sense at first.

lotusmark · Post by **lotusmark** » Fri May 01, 2009 10:02 pm

" I see, said the blind man , as he picked up his hammer and saw."

Ahhhhh! Thank You.

ScooterTrash · Post by **ScooterTrash** » Fri May 01, 2009 10:54 pm

djelliott wrote:
Lostmycage wrote:It looks more like a nail. I'll try and snap a shot of it... good grief my list of things to do is getting longer and longer.....

Here's what the needle looks like (not the same as ours, but it gives you an idea of why a washer (Radio Shack PN: 64-3022 - 100 pack assorted washers - $2) has to make due instead of a clip (no clip slots).
Nicely done pal. I feel like a tool for getting it wrong. What I did seemed to make sense at first.

Glad I didn't ask you HOW to do it

ScooterTrash · Post by **ScooterTrash** » Fri May 01, 2009 10:57 pm

lotusmark wrote:In polite response to Scootertrash. I'm no stranger to wrenching. My current Lotus has been modded to 225hp from a 1.8 NA. It weighs 1450 lbs without my fat arse in it and on the track will outhandle cars with twice the HP, just not in a straight line!

Sick car and props to you but this has absolutely nothing to do with tuning a scooter. Otherwise you would know to start rich and go down and you wouldn't be on here asking how. I also build track / auto-x cars and have yet to use anything that applied on my car for my scoot

[email protected] · Post by **[email protected]** » Fri May 01, 2009 11:07 pm

I know what you mean I can tune an old vw beetle but I still cant get my lawn mower or snowblower to work correctly

lotusmark · Post by **lotusmark** » Sat May 02, 2009 12:20 am

Sick car and props to you but this has absolutely nothing to do with tuning a scooter. Otherwise you would know to start rich and go down and you wouldn't be on here asking how. I also build track / auto-x cars and have yet to use anything that applied on my car for my scoot

[/quote]

You are absolutely right, and that is why I asked for help.

ScooterTrash · Post by **ScooterTrash** » Sat May 02, 2009 2:20 am

All I was saying is that carb tuning should not be learned via forums, I was taught by the mechanic at the sled shop in town. I personally won't give advice because someone could blame their mistake on me

Lostmycage · Post by **Lostmycage** » Sat May 02, 2009 7:21 am

ScooterTrash wrote:All I was saying is that carb tuning should not be learned via forums, I was taught by the mechanic at the sled shop in town. I personally won't give advice because someone could blame their mistake on me

That's actually a very good point. The only reason I'm so reckless with the Blur is because I had a back-up scooter (the Buddy 150) when I started getting into this nonsense and I paid about half MSRP for it used. I justify what I do in that "It's still cheaper than it would have been brand new".

Now that I've sold my Buddy, it's a little riskier; but I've also put in countless hours of research on the things that I do mod. There's not a single thing on my scooter that I haven't milled over for at least a month or two before knowing every possible detail available. There's still more surprises once you get into each project. The engineers that designed these scoots know their stuff. The PGO scoots are well thought out machines that are built to hop on and ride. Left stock and upkept with regular maintenance, they should last for many years.

The dark arts should be heavily considered and weighed before jumping in and throwing a bunch of stuff from who knows where into them. Understanding how to tune them should be the first step. Recognizing what each component does needs to understood before you start replacing perfectly good stock parts (they're for the most part bullet-proof) for "performance" parts.

My personal outlook on performance modding is that for every person that's impressed with what my little 150cc scooter will do, that's one more person who will be more aware of 2-wheelers on the road and maybe even get into this stuff and leave their regular cars at home. It's an efficient way to travel and it has many rewards.

In short it's not for everyone and any modifications should be carefully researched and thought out before hand. You should also keep in mind that this is the internet, sometimes people boast. Always do your own research and always get that from multiple sources.

I try to offer advice on things I know or have found out from first-hand experience, but I'm no expert by any means.

Think it through and ask yourself "Is this worth risking my beloved scoot based on what some stranger posted on an internet forum?" At first the answer should always be "NO!". Do your homework! Just make sure that you're still going to be able to enjoy your ride. That's the most important part.

Skootz Kabootz · Post by **Skootz Kabootz** » Sat May 02, 2009 7:48 am

Well said.

Personally, I would love to explore tinkering with my St. Tropez. Even just for the fun of tinkering if not for some specific performance upgrade. But I have to ask myself, is it worth possibly compromising how dependable, reliable, and consistent my scooting machine (and daily transportation) is as it stands? Better I get a second scooter [

] and play around with that one instead.

Kaos · Post by **Kaos** » Sat May 02, 2009 3:01 pm

ScooterTrash wrote:All I was saying is that carb tuning should not be learned via forums, I was taught by the mechanic at the sled shop in town. I personally won't give advice because someone could blame their mistake on me

Yeah, I gotta second that. I'll give tons of performance advice here, but carb tuning is kinda a dark art

I'm not saying don't give it a shot, by all means play with it if you're comfortable, but just don't say we didn't warn ya

I've been tuning Hotrod carbs since I was 12, so I've got years of tuning, and its still a pain in the butt. Carburetors are one of the most finicky parts of a motor.

lotusmark · Post by **lotusmark** » Sat May 02, 2009 7:46 pm

Would you guys explain your process for reading your plug.

Lostmycage · Post by **Lostmycage** » Sat May 02, 2009 8:44 pm

This is a snippet from the FAQ in progess. It's only for basic plug reading. there's no images quite yet

I've got my hands full today (Clutch install and pics, etc) so I don't have charts/pics to share at the moment.

Take the scoot out on an open road with a spark plug socket and Run it up to close to full speed. The idea is to get it to run the carb on the main jet (instead of the idle jet). Once you've ridden it at speed for a few minutes (don't break any laws or anything) pull over safely and shut it down. Give it a minute or so to cool off (or bring some mechanic type gloves) and pull the plug out. It's similar to a Plug chop for a 2T engine, but the goal is to get a reading on the main jet.

If it's ashy colored, then you're lean. (go up a jet)
If it's coffee/cream colored, you're just right.
If it's oily, you're too rich (chances are this won't be the case, it's just for reference).

Repeat until the plug reads the coffee/cream color. Note: iridium plugs are harder to read - they have a TINY electrode. Use a cheap fresh plug for this to get a good reading. I have a plug that I use just for jet tuning. At $3-5 it's not a hard hit on the budget.

Google NGK spark plug chart and you should stumble across a really good reading chart.

ALSO: If you're using a brand new plug, you'll want to ride it around for a good little while, at least 20 minutes of at speed riding. This will help avoid any false readings, etc.

Modern Buddy

Those Hoodoo carb Voodoo....

Those Hoodoo carb Voodoo....

Re: Those Hoodoo carb Voodoo....