Stupid Question RE: P Series carb Rebuild

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epsato
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Stupid Question RE: P Series carb Rebuild

Postby epsato » Mon Oct 01, 2012 1:15 pm

Got an Autolube carb I'm rebuilding...it's my first time rebuilding a P series Carb.

When reconnecting everything, the throttle cable goes THROUGH the Oil injector arm and then hooks onto the throttle slide hook, yes? I was all worried as the oil thingee has no spring, but it hit me that the throttle cable hooks up to the slide directly (nice big "duh" on that one). I'm pretty sure this is the set up, but figured it was better to ask ahead of time.

Also, I just took off the engine to install a new SITO+ exhaust (which it desperately needed, the old one was cracked where it meets the cylinder). While installing the new sito+, the cylinder shroud (it's a tube that connects to the exhaust) could spin as I attached the exhaust. Is this a bad thing? Can it mess with performance?

I'm worried the shroud will go into the cylinder. Normally the shroud's part of the cylinder and doesn't move, right?

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normratscoots
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Re: Stupid Question RE: P Series carb Rebuild

Postby normratscoots » Mon Oct 01, 2012 1:36 pm

A little confused with your question; the shroud doesn't need to be removed to change exhausts. The term applies to the large plastic bonnet the encases the cylinder and head. Are we talking about the same thing?

See this, for context: http://vespamaintenance.com/engine/decoke/index.html
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epsato
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Re: Stupid Question RE: P Series carb Rebuild

Postby epsato » Mon Oct 01, 2012 1:45 pm

Not the plastic shroud that goes over the cylinder. It's a little tube that connects to the exhaust from the cylinder.

The thing the exhaust clamps onto, what's that called? Anyway, mine seemed loose.

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Re: Stupid Question RE: P Series carb Rebuild

Postby epsato » Mon Oct 01, 2012 1:48 pm

Image

I'm talking about that cylinder on the left. Is it okay if that thing turns? I am used to the part being fused on and unmovable...

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normratscoots
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Re: Stupid Question RE: P Series carb Rebuild

Postby normratscoots » Mon Oct 01, 2012 2:43 pm

Exhaust stub or flange. No, it shouldn't be loose. It should thread into the cylinder until firmly in place.
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epsato
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Re: Stupid Question RE: P Series carb Rebuild

Postby epsato » Mon Oct 01, 2012 2:57 pm

Okay, gotcha. It's in there firmly now, but I was worried it would slide into the piston...

RE: the carb, I pull the end of the throttle cable THROUGH the oil channel's arm and then hook it to the slide, yes?

Just want to be sure I'm doing this right.

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normratscoots
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Re: Stupid Question RE: P Series carb Rebuild

Postby normratscoots » Mon Oct 01, 2012 3:32 pm

That sounds right (having trouble visualizing it). It should be a straight-foward fit.
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Mikeh
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Re: Stupid Question RE: P Series carb Rebuild

Postby Mikeh » Mon Oct 01, 2012 4:43 pm

The stub for the exhaust THREADS into the cylinder. there are fine threads on it that need to be clean to fit correctly. Then at the other end there is usually notches cut into it that you can use a heavy bar of steel or a wrench to turn the stub until it's in there and tight. You definately don't want to be able to just pull the stub out.

The L shaped thing on the carb fits into the hole on the autolube arm, then the cable fits to the autolube arm.

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Re: Stupid Question RE: P Series carb Rebuild

Postby epsato » Mon Oct 01, 2012 4:50 pm

Mikeh wrote:The stub for the exhaust THREADS into the cylinder. there are fine threads on it that need to be clean to fit correctly. Then at the other end there is usually notches cut into it that you can use a heavy bar of steel or a wrench to turn the stub until it's in there and tight. You definately don't want to be able to just pull the stub out.

The L shaped thing on the carb fits into the hole on the autolube arm, then the cable fits to the autolube arm.



I was worried you'd say something like that. I tigthened it a bit before attaching the sito. The sito was replaced because the scoot had been "running" a bit. If I ever gave it more than 50% gas, it wouldn't stop! I figured this meant an air leak somewhere. Since the old SITO+ had a crack in it where it met the cylinder, I figured this might be the source of the problem. But perhaps it's because it wasn't well enough attached...

Man, as if it wasn't a bear to remove the engine on Saturday when I had a friend over, it's going to be a total PITA to do it now...depending on how it goes, I may get stuck riding up on the PX again. D'oh!

RE: the carb, thanks for the heads up. I knew they were connected but couldn't remember how...

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Mikeh
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Re: Stupid Question RE: P Series carb Rebuild

Postby Mikeh » Mon Oct 01, 2012 5:10 pm

You should not need to remove the engine to get the stub to thread in there. But you may need to get a wire brush bit for a dremel and a can or carb cleaner and clean the threads in the cylinder up read good before attempting to thread the stub into the cylinder. And of course you need to clean the threads on the stub while it is out. The old sito probably cracked because it was bodged in there.

If you thought jambing the stub into the cylinder was good enough then you have a lot to learn about wrenching. That shit needs to be solid.

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Re: Stupid Question RE: P Series carb Rebuild

Postby epsato » Mon Oct 01, 2012 5:12 pm

Wouldn't I need to remove the sito+ to get to the stub? I wasn't able to get the exhaust off without removing the engine.

I'll be the first to admit there's plenty I don't know about wrenching :)

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Re: Stupid Question RE: P Series carb Rebuild

Postby epsato » Mon Oct 01, 2012 5:28 pm

Just saw on Vespa Maintenance...I can do all this by simply removing the rear tire. Am I on the right path?

I don't have the goods to rework the threads, but if I clean them and then tighten it back onto the cylinder, I presume that's better than doing nothing? The impression I get's that this is more on the "need to do" rather than the "probably need to do" order of things...

Frack me did I waste a lot of time on Saturday replacing that sito! Oh well, live, learn, then ask on WMASA and get taken to task for not asking beforehand...

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Mikeh
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Re: Stupid Question RE: P Series carb Rebuild

Postby Mikeh » Mon Oct 01, 2012 5:52 pm

You need to get it threaded up in there at least one or two full turns worth. Basically you need to NOT be able to pull it back out and be sure that it won't vibrate out.

FYI, I broke my JL performance exhaust mount at the swingarm three times because my connection at the cylinder stub was not tight. On a JL the pipe is held onto the stub with springs. Well, when I revved the engine the pipe stub would vibrate outward with the pulsing of the 2 stroke engine. After hundreds of miles this would eventualy crack the pipe support at the swing arm. It seemed to do it on every distance race for the first couple of races. The last time it held together but still cracked the bracket.. so I welded the bracket once more but then used more strategically located springs and stopped the vibrating stub, and the problem was solved.

I have a feeling this same type of vibration is what did your old sito in. And it also will improve performance if you have no leaking (the leaking is secondary in importance to the hammering that the 2 stroke pulses will have on your exhaust.

You need to be able to rev the piss out of the motor and watch the exhaust to see that it does not bounce around. If you accomplish this then you should be good to go.

Cleaning the threads on a stock cylinder is not hard, but it's a pain to remove the carbon build up. And I'll bet you have plenty of carbon build up since it was not threaded in there before so the threads were not protected. AND to make it worse your stub was likely bouncing around in there for a long time, so it may be likely that your threads are damaged. If your threads are toast then your only option may be to grind the threads of the stub off and then weld a couple of rings to the exhaust and use springs to hold it tight ot the cylinder like a performance pipe.

Good luck and I hope you can get it screwed in there a couple of turns. The other option seems a little daunting.

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Re: Stupid Question RE: P Series carb Rebuild

Postby epsato » Tue Oct 02, 2012 10:48 am

Good and bad after wrenching:

Realized I need to replace the rear brake cable. It's totally shredded and won't go through the hole. Likewise one of the gear shift cables. I'd marked them, but sure enough it rubbed off after I'd done my ill advised engine removal. Will be replacing cables this evening.

I'm not 100% sure if I kept my rear brake cable or gave it away. If I still have it, easy fix.

Carb was rebuilt and re-attached. got it up and started with the carb box top off. Popped the top on and it won't start. Flooded the engine, and I saw some leaking. Am going to remove the carb and double check to make sure the screws are on well, all grommets and gaskets r well placed, etc. I also thought about running with the box open, but is that advisable?

With luck, that's all it'll need to get up and running. With the new Sito+ the engine sounded solid...just gotta see if i can get it to start and run consistently enough to take it on a long ride + weekend o' partying...

epsato
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Re: Stupid Question RE: P Series carb Rebuild

Postby epsato » Tue Oct 02, 2012 10:51 am

After i give this a serious run tonight, anyone free on Wednesday or Thursday to come by for a bit with advise/feedback?


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