was 130 DR loss of power - now CP21 jetting
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Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
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Wed Dec 13, 2017 7:59 am quote
So yesterday I had my PV out several times. In the morning I had some higher idle which I had attributed to cold weather coming on and need to adjust the clutch cable (drags the RPM up a bit while slowing down, etc.). I did cut my idle air down when I stopped to park - a bit too much as I learned when I went to restart it and it wouldn't run. So I raised it back up until it was able to idle, no problem. On the way to my gym up a huge incline, I usually barrel up in 4th WOT with no issues. But this time I had it bog down after a bit and lose power. There was no high temps or anything (340F / 170C on the stud mounted CHT). I clutched it and blipped the throttle, no problem, it kept running. This happened a couple times then it was squared away after I pulled over and gave it a second. So I got to thinking about air leaks.

Before I left to go home I threw in a new plug and it rode home fine no issues. Idles were decent, no racing RPM, power was good, temps normal for this bike.

At home I let the engine down for a look for leaks.
-Carb is Polini CP21 direct mount to the manifold, was tight and no sign of leaks.
-No sign of leaks at intake manifold and nuts tight
-No sign of leaks at exhaust manifold and nuts tight
-No sign of leaks at head to barrel and nuts tight

Anything else I should be checking? I'm wondering if I just had some crap in the carb as the bike had sat for 3-4 weeks, and we have that oh so lovely ethanol in our gas.

Thanks for any ideas. I'd rather check it all before sending it back out into the wild again. I did clean up my engine and adjust my cables well while doing my inspection.

This carb does have massive spitback, and I'm wondering if the soaked air filter might also play in.

Last edited by sdjohn on Sat Apr 14, 2018 6:22 pm; edited 1 time in total
Addicted
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Wed Dec 13, 2017 8:16 am quote
I have had problems with oiled air filters on modified smallies...I prefer the dry type or just a bell mouth...

Other than that, keep riding and see if any symptoms reoccur...
Ossessionato
1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
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Location: So Cal
Wed Dec 13, 2017 8:46 am quote
My CP spits and drools like a madman... I never could get it to run right with a filter. I run it with no filter now, much better.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
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Thu Dec 14, 2017 3:48 am quote
How does the plug colour look after a WOT run?
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Thu Dec 14, 2017 5:06 am quote
Not a plug chop but is the plug that came out. They are hard to photograph, the flash makes it appear lighter than it is.

76D7F68A-11D6-4544-BDB3-914B18E741DF.jpeg

Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Thu Dec 14, 2017 5:07 am quote
Another

7948FAAD-4649-44CC-9B61-65813C71B4E9.jpeg

Molto Verboso
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Thu Dec 14, 2017 6:00 am quote
Looking like the main jet is about right but the pilot jet or atomiser (or both) are too rich.
Don't know a great deal about small frames but carbs I have a good idea about.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Thu Dec 14, 2017 8:06 am quote
Yeah the polini cp21 has only 2 possible needles, this one and a richer one. I’m on 2nd clip, I can use 1st and have sometimes. I don’t think there are atomizer choices but there is a brass plug that can be subbed out for one with a hole to lean out the atomizer. I have that somewhere.... the bike has run rich but been reliable.
Molto Verboso
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Thu Dec 14, 2017 9:24 am quote
The part that the needle runs in needs to be smaller. If you have one with a smaller hole through it put that one in.

You may need to raise the needle and up the main jet as required, to get it back where it is now but the result will be leaner at lower throttle, where it is currently way over.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Thu Dec 14, 2017 10:40 am quote
the air brake jet is what I have:



As to what that is:



9. THE ATOMOZIER AND AIR BRAKE

The atomizer is a tube that connects the main jet to the venturi and it is called “two-stroke type” when it doesn’t have any hole. Otherwise if it has a series of holes along its entire length it is called “four-stroke type”.(Attention: to call the atomizers “2 or 4 stroke” is popular but technically incorrect because you can safely use atomizers with holes for the 2 stroke too. I.e the Minibikes have atomizers with “4 stroke” type holes). Its working is very easy: due to the depression in the venturi then, from the atomizer tube the liquid fuel is drawn, metered by the main jet and by the conical needle, while a certain airflow comes from the channel. Air and fuel mix together and the result is a pulverized spray sucked by the engine. To intervene in this process, in addition to the atomizer hole, there are the air channel diameter, the height of the part of the atomizer protruding into the chamber and the height of the step located in the nozzle. In addition to the atomizer’s hole diameter, the variables are therefore the diameter of the air channel, the height of the atomizer’s side that protrudes in the chamber and the “step” of the delivery nozzle. The “four stroke” type produces leaner mixture and more controlled; in fact since it is equipped with a series of holes the emulsion is done inside the tube, before the mixture reaches the nozzle in the venture. Obviously the arrangement of the holes and their diameter influences the delivery. Holes machined in the lower part of the atomizer are bathed in the fuel of the bowl so, by increasing the numbers of holes the flow of fuel increases and goes to emulsify itself with the air. The holes in the upper part of the atomizer are exposed to air and by increasing them you obtain weaker carburation at low rpm.
The POLINI CP carburetor can be adjusted so that it works with both the types, 2 or 4 stroke, changing the brake air jet.

Close air brake jet: 2 stroke atomizer type working as an atomizer without holes
Open air brake jet: the atomizer holes work and make the engine weaker.

Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Thu Dec 14, 2017 10:51 am quote
As for the atomizer and atomizer bush, shown in the diagram below, there is only one atomizer per carb size and of the 2 bushes I have the bigger one based on the parts list for the carb I bought.

cp21.jpg



Last edited by sdjohn on Thu Dec 14, 2017 10:59 am; edited 1 time in total
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Thu Dec 14, 2017 10:53 am quote
parts list for what comes in my carb from the factory

cp21_2.jpg

Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Thu Dec 14, 2017 10:55 am quote
Jack221 wrote:
The part that the needle runs in needs to be smaller. If you have one with a smaller hole through it put that one in.

You may need to raise the needle and up the main jet as required, to get it back where it is now but the result will be leaner at lower throttle, where it is currently way over.
Aha, now I see this is possible - I can get the 2.6mm bush.
Molto Verboso
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Thu Dec 14, 2017 11:43 pm quote
If you have the 2.7mm (270 in dellorto speak) then the 2.6 might be more appropriate.

Appears that you might have an atomiser with holes in the sides like a 4 stroke tube does (this makes it into an emulsion tube like the SI carb). I would say that this carb gets away with having only 2 atomisers due to the 4 stroke holes as the air brake jet (often not adjustable on other carbs) can be used to fine tune each atomiser.

The rich or weak point of an atomiser is set at just over 1/8 throttle. When riding at this throttle position on this CP21 carb you would tune the air brake jet to get the mixture right. If running on the 2.7 atomiser and when the air brake gets to 1.0 and its still too rich, then restart at to 2.6 atomiser and air brake at 0.0 and continue the increasing of the size of the air brake to weaken the atomiser function, until riding at 1/8 throttle is clean and crisp.

A more simple carb but appears to have all bases covered
Ossessionato
1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 4603
Location: So Cal
Fri Dec 15, 2017 6:13 am quote
Hey John, where are you getting parts for your CP?
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Fri Dec 15, 2017 7:51 am quote
Treatland gets them in socal. I ordered the 2.6 bushing yesterday and it's already shipped .

Thanks for the insight Jack. I will try out the air brake jet first and then possibly the bushing after, depending on the results. It's been pig rich in the low throttles since I put it on, looking forward to the improvement.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Fri Dec 15, 2017 7:59 am quote
BTW socal - if they don't have it on the web site they will order it for you. I think I had to have them order the leaner slide that I tried at one point and maybe the air brake jet also. The bushing was in stock yesterday, though. So ask if you can't find it.
Ossessionato
1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 4603
Location: So Cal
Fri Dec 15, 2017 8:09 am quote
Thx, mine's rich down low too... it's kind of a dog off off the line, then kicks in with more throttle... but I'll wait and see if that smaller bushola polverizo thing works for you before I order one.
Molto Verboso
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Fri Dec 15, 2017 9:24 am quote
Happy to help.
'Pig rich low down' does sound like more than a tweek with the air brake. If you dont have the 1.0mm air brake, just run the 2.7 atomiser bush without any airbrake fitted. If still rich, then you know it has to go to the 2.6mm bushing.

Be aware that, once you go to 2.6mm atomiser bushing, it is highly likely you will need to move the clip down and up the main jet too or risk being too lean at WOT.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Fri Dec 15, 2017 9:42 am quote
Thanks, it's no problem I have a load of main jets so will definitely keep that in mind. I can't remember how big of air brake jet I bought, it's been a while. I'll dig it out. It's harmless to try it first, so I will just to see the size of the effect.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
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Posts: 3677
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Sat Dec 16, 2017 5:42 pm quote
Looks like the air brake jet I have is 0.3mm. I may try it anyway.
Ossessionato
LXV 150 Midnight Blue (SOLD)
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Sat Dec 16, 2017 6:35 pm quote
Quote:
I usually barrel up in 4th WOT with no issues. But this time I had it bog down after a bit and lose power
The first "rule" of troubleshooting is : "What has changed?"

In this case?
Quote:
...I had some higher idle ... I did cut my idle air down when I stopped to park..
So my theory? Idle speed on some NSM Vespas can be as high as 1850 RPM. So if you readjust the idle with the air screw back to something like that you may find the problem goes away?
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
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Posts: 3677
Location: San Diego, CA
Sat Dec 16, 2017 7:02 pm quote
Yeah I raised it up again before I even got going and had the 4th gear issue, but I was still pointing it out because I was unsure about air leaks. I think there aren’t any based on the inspection.
Ossessionato
LXV 150 Midnight Blue (SOLD)
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Sat Dec 16, 2017 7:15 pm quote
Spray WD-40 all over it. If there is a leak it will suck the WD-40 in and you can see it.
Molto Verboso
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Sat Dec 16, 2017 11:33 pm quote
sdjohn wrote:
Looks like the air brake jet I have is 0.3mm. I may try it anyway.
2.7mm atomiser bushing and 0.3mm air brake gives you one setting from the richest low throttle that that carb can possibly deliver. I think this explains why the 'pig rich' at 1/8th throttle.

Take out the air brake jet completely and give it a ride. I expect it still to be slightly too rich.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Sun Dec 17, 2017 1:14 pm quote
Thanks guys. If the lean behavior returns Ihave no qualms on trying the WD40. I can try opening the air brake jet too. Right now I have the closed one on but can either go 0.3 or open as suggested. The 2.6 bushing showed up. Stay tuned.
Molto Verboso
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Mon Dec 18, 2017 5:12 am quote
On my smallie, also DR 130, I've had the kind of behavior exhibited in the original post due to low fuel level in the float bowl. Acts kind of like the increasing idle speed when turning off the fuel tap and allowing the engine to die. Shows as power loss while cruising, especially up grades. Hard to diagnose. Scratched hands and head. Pecking on the carb bowl way down there made it run, also an external tank on the seat for increased gravity feed. Sticking float/needle/seat? Carb removed, inspected, replaced, cured. Don't really know why.

In hot weather, I've also had vapor lock due to running the fuel line over, rather than under, the fuel tap shaft. The bubble in the fuel line was clearly visible. The fuel line over the shaft would not let the bubble rise up to the tank and out the breather tube. Pouring water on the line made the bubble go away, fuel flow resumed.

It would be nice to have a sight, drip hole, or other easy method for checking float level as in some carbs.
Ossessionato
1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 4603
Location: So Cal
Mon Dec 18, 2017 5:50 am quote
What would be nice to have is a clip in fuel tank. Pulling the smallie's carb is a chore.

Jack, thanks for explaining the air brake/atomizer on the CP. Polini's description isn't the clearest. I think I get it now. The air brake nozzle controls air flow over the holes in the atomizer. A larger air brake opening (or removing it completely) should lean out early throttle. I'm going to give it a try.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
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Posts: 3677
Location: San Diego, CA
Mon Dec 18, 2017 6:47 am quote
Good ideas blackbart, thanks. I will keep them in mind as I go at this again.
Molto Verboso
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Wed Jan 10, 2018 12:47 am quote
Did you try the 2.6 atomiser?
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
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Wed Jan 10, 2018 6:10 am quote
Not yet, the P200 has all my attention right now.
Hooked
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Thu Jan 11, 2018 9:35 pm quote
Just thinking....
What's your ignition set up?

Just thinking of alternatives if the carb doesn't pan out.

I'm no help on the C P. I've always run mikuni on my Primi 130.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
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Fri Jan 12, 2018 6:52 am quote
Stock ignition and flywheel, though the flywheel has been lightened.
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Fri Jan 12, 2018 9:15 am quote
sdjohn wrote:
Stock ignition and flywheel, though the flywheel has been lightened.
Points and Condensor? I've had issues with losing power at the top of the rev range with a bad condensor before.

My first thought would be to the carb and wet filter. But stock ignition parts are cheap swaps.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
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Fri Jan 12, 2018 10:10 am quote
Ride like a champ last time I had it out, but jetting still needs attention.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
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Sat Apr 14, 2018 6:29 pm quote
Couple of quick trials today.

First - remove air brake and ride - way too lean across the spectrum, idle racing, high temps, not pretty.

Second - same as above but move from 2nd clip from top to middle clip. This was better but still felt lean on the top end. It's clear the added air to the atomizer affects the whole range based on the behavior.

Third - reinstall air brake and swap from 2.7mm needle bushing to 2.6. Increase main from 95 to 100. Needle on middle clip. This feels pretty darn good. Main may drop from 100 to 98 but I'll take a few longer rides to decide. I was able to adjust the idle to work fine with the jet that's in there (36? I can't remember, would have to check the old notes). This is a good sign, as before the idle air mix screw really didn't do much, and now it actually changed the mix and dropped the revs. It's idling pretty good, I'll have to count the turns out and see if it needs to go up one jet size but for now it is working. What I like is that now it seems there is room to adjust things, whereas before I was out of adjustment on several items (I didn't want to go first clip, the idle adjustment wasn't very responsive, etc.). For now most of the range felt pretty clean. It's a bit mild at the moment, it's always more telling when it's 100 degrees out or 40 degrees out.
Molto Verboso
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Sun Apr 15, 2018 11:40 pm quote
I see you are getting some practice in on the smallie

Here are a few pointers that you may or may not know already but make setting up a needle carb quicker.

Leave the main jet very much way to big until the atomiser and needle are set.

Set the pilot jet until you have a feeling that it is very slightly weak (like one size too small). Nothing bad will happen. Come back to this at the end when everything runs well. If the pilot jet is even slightly too big it just gets too confusing and distorts the whole set up.
When the pilot jet is good, run down return to tickover feels and sounds nice when very hot. So slightly weak should feel a bit 'fluffy' at this point for now. Check the hot 5 minute re-start after riding, is immediate….like half a kick, if set correctly (or weaker).

The atomiser is easiest set at 1/4 throttle. Change the atomiser, air brake and or needle diameter when at 1/4 throttle, to get 1/4 throttle running perfect, while forgetting about everything else. Do not touch the needle clip (set at 3), main jet or pilot while doing this.

Its always necessary to go round the bases several times before a carb is set up. Done right it gets ever closer to correct. Get something wrong it becomes confusing and over sensitive.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Mon Apr 16, 2018 7:12 am quote
Thanks Jack, those are great tidbits.

Had it out for a good go this morning. Looks like I got the main and needle pretty darn close, temps are no higher than the old setup but power seems improved. The lower throttles felt pretty clean, we will see how they do in the heat of the day later. I overachieved on the small pilot jet, as it was staying at pretty high engine speed after a long WOT section - that's with no throttle. I adjusted the air screw and throttle opening to compensate for now, but it definitely would like a 38 instead of the 36. As added confirmation the bike took 6 kicks to start instead of its usual 2, so I had a feeling the pilot was too small.

And you're exactly right - this is the warmup act for the P200, where I get my bearings before going in on the more expensive bit of kit.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3677
Location: San Diego, CA
Mon Apr 16, 2018 7:30 pm quote
38 pilot installed. The float was a leaker on one side, installed my spare. Will have a go and report back. The main is pretty good, after I try the pilot I will try to go up and see if it loses mojo. My guess is it can go down to 98 but I need to feel it rich first to make sure that I’m on the right side of it. Definitely was lean at 1/8 throttle.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
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Tue Apr 17, 2018 12:19 am quote
Not starting well cold is a good sign the pilot is weak. If the pilot is rich it is near impossible to set the atomiser, which affects everything, then the whole set up is a mess. Being sure the pilot is just slightly weak is the key.

If now it is running clean and smooth from tickover to wide open, starting well hot and cold, then the fun part begins.

As you have started doing, the leaning out to where the best power is the next step. This is the part where most crap themselves and start making up their own rules and excuses!

Fit a main jet that will splutter very bad at WOT, then down to one that will just splutter at WOT (this may seem pointless but it really isn't), then back off one more whole jet size. Next lean out the needle clip, half a clip at a time (should be on clip 3 at the moment) until it pulls hard at 1/2 throttle and will cruise at half throttle for several miles without seizing. Then back to the main jet and drop yet one more jet size.

This will be it for a few weeks riding until you decide how well it runs.

Doing it correctly is how to do it quickly. it takes years to be any good and the noises to listen for and the checks along the way but this will get you on the right track
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