Throttle issues before and after carb rebuild

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Sevyndaze
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Throttle issues before and after carb rebuild

Post by Sevyndaze »

Hi everyone,

So I've been in the process of fixing a whole bunch of stuff on my 2001 elite S (derestricted), including rebuilding the carb. I followed this guide to the letter http://hondaspree.net/wiki/index.php5?t ... ture_Guide. It starts right up, and idles smoothly around 1400 RPM assuming i've got my tachometer on the right setting.

The problem is that once I take the rear brake off, if I twist the throttle (or sometimes even if I don't), the engine will just arbitrarily race away. It would do this before I tore it down when I first started it, but would stop after the engine got warmed up. I figured whatever the issue was I'd solve it by rebuilding the carb, but no dice. Any ideas? I haven't let it idle long enough to see if it will calm down on its own like it used to, but since I'm pretty sure it's not supposed to do that at all, I'd rather just find the root of the problem and fix it. Any advice you scooter gurus have to offer would be very much appreciated. Thank you!
2001 Elite S (Derestricted)
Arrow Exhaust
Polini Variator
6.9g rollers
ZX Trans
1.5k Contra, 4k shoe springs
16/42 Gears
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motormike
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Re: Throttle issues before and after carb rebuild

Post by motormike »

Sevyndaze wrote: the engine will just arbitrarily race away.
This symptom is the number one thing that indicates a vacuum leak.
Bad O-ring on carb flange, or insulator, or whatever is associated with your intake set-up.
Plenty of possible points to fail...not familiar enough to list them... :urban:
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Sevyndaze
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Joined: Sun Jun 10, 2018 3:43 pm
Location: New Hampshire

Re: Throttle issues before and after carb rebuild

Post by Sevyndaze »

I replaced the intake gasket along with all the other gaskets when rebuilding the carb. Anything else that should be looked at?
2001 Elite S (Derestricted)
Arrow Exhaust
Polini Variator
6.9g rollers
ZX Trans
1.5k Contra, 4k shoe springs
16/42 Gears
Sevyndaze
Spree
Spree
Posts: 114
Joined: Sun Jun 10, 2018 3:43 pm
Location: New Hampshire

Re: Throttle issues before and after carb rebuild

Post by Sevyndaze »

UPDATE: I may have gotten it figured out. I decided to have another go at tuning it before nightfall. I think I had my tach on the wrong setting so it was actually giving me half the RPM of what the engine was actually running at. I'm not sure how many pulses per cycle the elite gives. Per the instructions that came with the tach it seemed like it would be 2 per cycle, but when I set it to 1 pulse per cycle those numbers seemed to make more sense. I wound the mix screw all the way in, then backed it out 1 and 7/8 terms, per the service manual's instructions for the SA50. I put the throttle stop screw where it was before I tore it down (at 3/8 turns out), then started it. I adjusted the throttle stop screw so it idled between 1800-1900 rpm, moved the mix screw to the highest RPM point (within 1/4 turn max in either direction, again, per the service manual), then adjusted the idle screw so it ran at just over 1800 RPM.

It could just be that the engine warmed up sufficiently to stop racing (like it did before I tore it down), so I'll give it another go in the morning and see if it still behaves itself.

For reference, the current configuration is as follows: Stock exhaust with restriction washer removed, stock airbox with blocked tab removed and brand new, freshly oiled filter, new, properly gapped BPR8HSA plug, and a freshly rebuilt stock carb with a #78 jet.
2001 Elite S (Derestricted)
Arrow Exhaust
Polini Variator
6.9g rollers
ZX Trans
1.5k Contra, 4k shoe springs
16/42 Gears
Sevyndaze
Spree
Spree
Posts: 114
Joined: Sun Jun 10, 2018 3:43 pm
Location: New Hampshire

Re: Throttle issues before and after carb rebuild

Post by Sevyndaze »

UPDATED UPDATE: We are officially rolling! Went for a short ride to warm it up so I could tune the carb properly, no issues. Tuned the carb and made about a 5-mile round trip into town and back to fill up. GPS confirmed 38.5 on a slight decline. Didn't get a good number for a true flat but it looked like about 35.
2001 Elite S (Derestricted)
Arrow Exhaust
Polini Variator
6.9g rollers
ZX Trans
1.5k Contra, 4k shoe springs
16/42 Gears
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Meatball
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Re: Throttle issues before and after carb rebuild

Post by Meatball »

Use a sharpie marker and draw lines on the variator face all the way to the outer edge. Then reassemble and got for a few WOT runs on flat to achieve the scootÔÇÖs maximum speed. Then check variator lines to see how high up the belt gets at full tilt. You should be doing 40 on a derestricted stock motor on flat all day. Report back results.
I need to find some new haters...the ones I have are starting to like me.
Sevyndaze
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Re: Throttle issues before and after carb rebuild

Post by Sevyndaze »

Sounds like a good project for Wednesday when IÔÇÖll have the day off from work. IÔÇÖll give it a go.

One thought: a derestricted S still has a different variator ramp and final gearing than an SR, right? Could that be the reason for the difference? Or would a stock SR go even faster than 40?
2001 Elite S (Derestricted)
Arrow Exhaust
Polini Variator
6.9g rollers
ZX Trans
1.5k Contra, 4k shoe springs
16/42 Gears
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Meatball
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Re: Throttle issues before and after carb rebuild

Post by Meatball »

Both the ÔÇ£SÔÇØ and ÔÇ£SRÔÇØ have the same 12.1:1 ratio and also the same variator. The S model just has a restrictor plate.
I need to find some new haters...the ones I have are starting to like me.
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Re: Throttle issues before and after carb rebuild

Post by Sevyndaze »

Thanks. I checked out the wiki and found this page http://hondaspree.net/wiki/index.php5?t ... ion_Ratios
Is the difference in the variator specs listed simply due to the restrictor plate?

IÔÇÖm also not exactly a small dude, about 230 lbs; maybe itÔÇÖs just having trouble pushing my fat * lol.

HavenÔÇÖt done the sharpie thing yet, will do that tomorrow. I was out on some WOT runs last night (of course I forgot my phone) and noticed that the RPMs got into the upper 8K range and even crossed 9 briefly. Is that normal?
2001 Elite S (Derestricted)
Arrow Exhaust
Polini Variator
6.9g rollers
ZX Trans
1.5k Contra, 4k shoe springs
16/42 Gears
Sevyndaze
Spree
Spree
Posts: 114
Joined: Sun Jun 10, 2018 3:43 pm
Location: New Hampshire

Re: Throttle issues before and after carb rebuild

Post by Sevyndaze »

Hey Meatball, here's the picture of my variator following your sharpie suggestion and a few WOT runs. Had some family over on Wednesday so I didn't get around to doing the test. Managed about 37 on a flat run.
Variatormarks.JPG
Variatormarks.JPG (149.82 KiB) Viewed 5729 times
Seems that the belt is not winding all the way out, unless this is a normal test result. Could this be due to flat spots on the rollers, or perhaps a worn belt? I also measured the belt width while I had the covers off, the flat side was approximately 5/8" and the toothed side was about 7/16". I don't have calipers so I had to use a tape measure and eye it the best I could.

Also, I am curious what the highest safe RPM is for this engine...the tach I have has shown over 9000 on a few occasions.
2001 Elite S (Derestricted)
Arrow Exhaust
Polini Variator
6.9g rollers
ZX Trans
1.5k Contra, 4k shoe springs
16/42 Gears
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Wheelman-111
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Re: Throttle issues before and after carb rebuild

Post by Wheelman-111 »

Greetings:

That looks pretty good. The shape of the outer sheave limits the belt travel so I don't think it EVER completely erases the Sharpie marks at the rim. The air-cooled Honda engines can spin to 10K or above safely, but often won't because of the port timing. They run out of breath...
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
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Re: Throttle issues before and after carb rebuild

Post by Sevyndaze »

Thanks Wheelman. Still would like to be able to hit 40 if that's what the bike should be capable of. Could it be a carb-tuning issue, or perhaps flat-spotted rollers? I've been toying with the idea of getting a new variator; it seems like that would offer the biggest "bang-for-the-buck" increase in acceleration and top speed now that the bike has been de-restricted.
2001 Elite S (Derestricted)
Arrow Exhaust
Polini Variator
6.9g rollers
ZX Trans
1.5k Contra, 4k shoe springs
16/42 Gears
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Wheelman-111
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Re: Throttle issues before and after carb rebuild

Post by Wheelman-111 »

Greetings:

Brand-spankin' (35 miles) NEW Flash 3 went 49 (OK, Downwind...) with nothing but bigger 90/90 tires, a Polini variator, and 9.1:1 gears pressed in. Engine itself was UN-Touched at the time.
"Tuning" the carb isn't likely to help; it needs a 78 main and bigger or smaller mean slower. Make sure your air box has a healthy filter and your exhaust isn't caked with Carbon. A new spark plug wouldn't hurt. While it's off, verify compression - a 10-minute operation - to see if the top end is still healthy. An air leak anywhere is a performance killer, and could mean Sudden Death.
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
Sevyndaze
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Location: New Hampshire

Re: Throttle issues before and after carb rebuild

Post by Sevyndaze »

Yep, carb is squeaky clean with a 78 jet, new air filter and a new spark plug. ItÔÇÖs basically just de-restricted to match the specs of an SR. I think the tires are 90/90 but not totally sure.

How was the acceleration with the taller gears? Still manageable for city traffic?
2001 Elite S (Derestricted)
Arrow Exhaust
Polini Variator
6.9g rollers
ZX Trans
1.5k Contra, 4k shoe springs
16/42 Gears
User avatar
Wheelman-111
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Re: Throttle issues before and after carb rebuild

Post by Wheelman-111 »

Greetings:

No issues in traffic at all. Probably a bit slower from 0-5, but that's the beauty of the variator - you'd need a stopwatch to tell the difference. With a larger ZX rear pulley and drive train, it's back to just-as-fast.
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
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