OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
 
Hooked
@spacecat avatar
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
UTC quote
Status update

OK, so I have been in denial that I could have an air leak at the carb because for years I have taken the carb off and replaced it with no problem. But I recognize that's no basis for ignore that possibility, so I went ahead and tried blue RTV in the manifold and carb slits. Let it sit for a day and then started it up. It is better -- it now idles instead of racing, but with the choke on. I can't get it to keep running with the choke off.

So I then tried adding a ground to the frame on the CDI (per Ginch's post) -- I already had it grounded to the engine. No difference, but worth the try and possibly saving me some mysteries down the road anyway.

Then I checked the torque. Well, so much for being worried about 10 ft lbs. Somewhere I got a shop manual that states 1.3 to 1.5 kgm for crankcase halves, which works out to 9.4 to 10.8 foot lbs. So, I think I had already torqued to at least 10 ft lbs; at any rate, the nuts were more than 8 today when I checked.

Then I took off the carb and tried it again without the felt washer. No difference. I reinstalled with a new felt washer. No difference.

I'm going to sit on this until the weekend, but next steps I had in mind is to once again drop the engine, see if I can pressure test while still in the bike, and do the exhaust gasket over. I don't know if it will make any difference but at least I can check it off my list.

I am reminding myself:
1) different faults can cause similar symptoms
2) more than 1 issue could be at play.

What else causes lean symptoms?
@socalguy avatar
UTC

bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
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Location: So Cal
 
bodgemaster
@socalguy avatar
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: UTC
Posts: 7157
Location: So Cal
UTC quote
Quote:
… it now idles instead of racing, but with the choke on. I can't get it to keep running with the choke off.
Have you ruled out gunk in the idle circuit?

I'm sure you've cleaned the carb - but how well? It was probably sitting in a box somewhere while you had the engine out. Could have picked up particles or bits of garage crud. It doesn't take much to clog the idle jet or circuit.

Wouldn't hurt to give it another good cleaning. Most important - blow out all the openings with compressed air.
OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
 
Hooked
@spacecat avatar
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
UTC quote
SoCalGuy wrote:
Have you ruled out gunk in the idle circuit?

I'm sure you've cleaned the carb - but how well?
I ask myself this in the middle of the night. I've gone over it a few times, but just with canned carb cleaner. I'll give it another go with compressed air.
OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
 
Hooked
@spacecat avatar
Vespa Primavera 1974
Joined: UTC
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Location: Nebraska USA
UTC quote
I went ahead and bought a bucket of carb cleaner and gave the carb another go, on SoCalGuy's note, with compressed air too. It did improve. I can now get it to stay running without the choke on, so this is a major step forward.

But I couldn't dial in the idle. Somewhere I saw sdjohn advise someone to "rebuild it again" so I will. I also am reading up on all the Vape Sport timing advice and expect to come around with some questions soon, as I process that info.

Just a status update -- no new questions yet.
@chandlerman avatar
UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
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78 Days Since Last Explosion
 
Lucky
@chandlerman avatar
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
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UTC quote
The Vape Sport timing is pretty easy to get right. We can cross that bridge when you come to it, though.
UTC

Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: UTC
Posts: 4606
Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
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Location: London UK
UTC quote
Sometimes the pilot jets block in the tiny hole at the tip. The only way to clear it is to poke wire through it.
If you have another pilot jet, make sure it's clear and try that.
OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
 
Hooked
@spacecat avatar
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Location: Nebraska USA
UTC quote
getting there -- carb close enough for now, now to timing

The suggestions to go back over the carb, especially the idle circuit, were spot on. I took the carb apart again, and cleaned up an idle jet from an old carb and put that in there. I was then able to keep it idling without the choke and adjust the mixture screw. I'm getting pretty close.

Now I'm back to wrassling with the gear selector cables but have been able to ride up the block in first and second gears. It's not perfect yet. I have a new idle jet from Scooter Mercato to put in today, and I am going to work on timing.

It's the VAPE Sport ignition on a Malossi cylinder kit. I have a basic Polini pipe. The timing for the Malossi is 17 BTDC. I set this with a piston stop and paper degree wheel, and then checked it with a timing light at whatever RPMs it's idling at. As others found, the VAPE stator plate is super accurate -- my marks lined up perfectly.

So, per the VAPE instructions, I'm good to go -- but not really, maybe? I've read quite a few threads, so if there's another good one I missed, please share.

For example, Ray8 shared this method for setting the VAPE timing which is super straighforward:
https://modernvespa.com/forum/post2613554#2613554

But in this thread, people suggest that actually setting the static timing is not sufficient.
Dialing-in new Vape SIP Ignition?

I'm confusing myself reading these threads because people are using "advance" and "retard" in contradictory ways.

If I have the gist right, the timing can be moved closer to TDC at higher RPMs for better performance. To simplify, using the chart everyone is pointing in the threads above, I should set the 17 degrees BTDC at 2274 RPMs and/or 4579 RPMs (approximately), because as RPMs increase, the variable ignition will move the spark timing closer to TDC for a while before then moving it away from TDC (bigger numbers BTDC). (I'm avoiding saying advance/retard.)

If I have the gist right, can you share your technique? I mean the physical parts too -- like check timing, remove the rotor, adjust timing, reinstall rotor, check the timing, do it again, etc? [ETA, I forgot, will not have to remove rotor between timing adjustments on the VAPE.]

Thanks in advance. Or retard, depending on how you are using those words.
OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
Joined: UTC
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Location: Nebraska USA
 
Hooked
@spacecat avatar
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Joined: UTC
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Location: Nebraska USA
UTC quote
Made good progress yesterday, but have a ways to go.

It starts first or second kick and idles good once it is warmed up.

I got the clutch and gear shift cables close enough to take it for several test rides up the block. It sounds right and has great acceleration when I first shift it into gear, then is loud and loses power (this is four stroking, no?) until I give it more throttle. This is the same in first and second gear. So I think I need to move down a jet or two or three. (I'm starting at 94 with the new pipe but expect to end up in the mid 80s.)

It's still hard to shift, and noisier when in neutral with the clutch lever not engaged (clutch engaged?) than with the clutch lever pulled in. I think this is a symptom of the cable needing more adjustment -- it also wants to stall starting from stand still.

And I am still wrassling with the selector cables. This may or may not be the reason, but I think I cut the outers just a centimeter or two too short. They fit precisely in the adjusters at one end and the top hats but with no noticeable tension.

So I need to sort these things before I can take it out for a longer ride to see how the timing is going.
@orwell84 avatar
UTC

Ossessionato
Joined: UTC
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Location: northern New York
 
Ossessionato
@orwell84 avatar
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Location: northern New York
UTC quote
I find that the engine always makes more noise in neutral when the clutch lever out.

I started to have a lot of problems with a grabby clutch when I tried to adjust it to have a small opening at the lever. When I loosened it, it was perfect.
⬆️    About 1 month elapsed    ⬇️
OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
 
Hooked
@spacecat avatar
Vespa Primavera 1974
Joined: UTC
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Location: Nebraska USA
UTC quote
I know everyone is waiting on tenterhooks for the next installment of this tale.

The gear change cables have been the absolute worst part of this whole journey. I'd go out to the garage after work, spend an hour adjusting and test driving, repeat, with little progress. And in the mean time, other work around the house piling up. I had to take a break to install some kitchen cabinets and beat back the weeds so they look like a lawn from a distance.

I finally got some hemostats and did V oodoo's trick https://modernvespa.com/forum/post2625865#2625865 and got it a lot closer. Still some adjustment to go, but I'd describe the desired setting as, not so tight that you bump into gear, but almost.

I am getting there with the carb adjustments. It's still rough in the first part of first gear but when I open it up, response is instant and it picks up fast. I am still getting some fuel drip out of the tail pipe, so it's too rich, but I don't yet know if that's because of the air mix screw or the jet.

Right now, I have downjetted to 80, which solved the fourstroking problem described above. I'm keeping a close eye on it though. I was running an 80 (the carb is the Dellorto 19/19) before, with the stock pipe (but Malossi 133 kit). It's possible it was running rich then, and now that I have the Pollini pipe, 80 is right, but I haven't yet been able to take it for a longer ride to check, and I don't think I have the air mix screw dialed in yet anyway.

I need to get it registered in Nebraska (it's titled so no worries there) and insured so I can take it out for a proper ride.

The timing for this cylinder kit is 17 degrees BTDC. Right now, I have the SIP Vape Sport set to hit 17 BTDC at about 4579 RMPs. I think it's important to note that this is a readout of how the variable ignition plays out, and not necessarily instructions on exactly how people should set it up. I don't have a tach on the bike so I don't know what it looks like at high revs, or even how high I am revving.

I post this to see if anyone has thoughts about how the variable timing might be playing into the choppyness before WOT in 1st gear. When I get back from a trip, I will continue working with the air mix screw. My assumption is that where I have the timing is a reasonable enough starting point that it is not a major contributor, but I'd welcome advice and experience on either.
THE GRAPH edited to show my current set up.
THE GRAPH edited to show my current set up.
@chandlerman avatar
UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
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78 Days Since Last Explosion
 
Lucky
@chandlerman avatar
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
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78 Days Since Last Explosion
UTC quote
If you're at 17 BTDC at 4,800, then you're a couple degrees too retarded, which is probably limiting your top end RPM's.

If you touch timing, advance it a couple degrees and see if that helps with the top end RPM's. Watch your temps when you do it, too, and remember that changing timing will impact your jetting, so probably do it sooner than later if you're going to do it.

Funny thing is, I've found getting the gear shift cables to be more of a PITA on the smallie, but at the same time, much easier to get "just right" than on any of my large frames. Go figure.
@sdjohn avatar
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Johnny Two Tone
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
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Johnny Two Tone
@sdjohn avatar
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UTC quote
I wonder if your selector box isn't the hottest or aligned the best to your gears, adding to your adjustment woes. There's a thread around here where you check the cruciform alignment to the wear marks on your axle with the cases open and bare. Not helpful with an assembled engine, but at least you might catch my drift.
OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
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Hooked
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Location: Nebraska USA
UTC quote
I finally have the gear selector cables in pretty good shape. I think it could be 2% better but it's good enough for now. I greased up the bat wing and put the cover back on. I also put the damned seat latch pin back on, my last milestone.

It starts and idles easily, runs great up and down the block. I need to ride it more to check the jetting but I don't have Nebraska plates yet. I haaaate getting pulled over, not just because of the $ but because of the roadside judge/jury/executioner attitude in about 50% of these interactions.

But I'll take a risk on a short ride -- I want to drive over to the DMV for inspection and plates, which is 4 or 5 miles each direction.

If I've jetted too lean, what are the chances I find out on this ride?
@chandlerman avatar
UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
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Location: Nashville

78 Days Since Last Explosion
 
Lucky
@chandlerman avatar
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9979
Location: Nashville

78 Days Since Last Explosion
UTC quote
spacecat wrote:
If I've jetted too lean, what are the chances I find out on this ride?
Do you have a CHT?
OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
 
Hooked
@spacecat avatar
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
UTC quote
chandlerman wrote:
Do you have a CHT?
Nope.

(Supposing I had one, what would I watch for?)
@sdjohn avatar
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Johnny Two Tone
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
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Location: San Diego, CA
 
Johnny Two Tone
@sdjohn avatar
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Posts: 8552
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UTC quote
why not up the main jet for insurance?
OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
 
Hooked
@spacecat avatar
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
UTC quote
sdjohn wrote:
why not up the main jet for insurance?
I am thinking this is the best strategy.
@chandlerman avatar
UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9979
Location: Nashville

78 Days Since Last Explosion
 
Lucky
@chandlerman avatar
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9979
Location: Nashville

78 Days Since Last Explosion
UTC quote
spacecat wrote:
Nope.

(Supposing I had one, what would I watch for?)
You'd be looking for temps that were getting up over 350F. Assuming they stayed under that, you're in good shape (with some Special Case caveats, but don't worry about those for a normal ride).
@chandlerman avatar
UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9979
Location: Nashville

78 Days Since Last Explosion
 
Lucky
@chandlerman avatar
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9979
Location: Nashville

78 Days Since Last Explosion
UTC quote
spacecat wrote:
I am thinking this is the best strategy.
You might also discover that you were leaner than you thought.
OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
 
Hooked
@spacecat avatar
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
UTC quote
chandlerman wrote:
You might also discover that you were leaner than you thought.
Yeah, I guess I may as well build this ride into my testing. Why waste the opportunity.
OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
Joined: UTC
Posts: 225
Location: Nebraska USA
 
Hooked
@spacecat avatar
Vespa Primavera 1974
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Location: Nebraska USA
UTC quote
Taking out the carb is another least favorite task, but I did, and found I was running an 82 jet not an 80 like I thought. I was running an 80 before I added the VAPE ignition and Polini pipe, so I was worried that with the better exhaust it would be lean at the same jet.

For kicks, I put the 84 in, to remind me how bad the four stroking was. Pretty bad. I don't like to ride WOT in my neighborhood because people don't stop at stop signs. I put the 82 back in. It rides nice, but it does four stroke a little at some points.

I have advanced the timing slightly, from what I am marking as 17 to max out at about 19 before it retards.

The explanation I have read about four stroking relates to scavenging and other things I don't bother to think about. As I understand it, the short of it is that making it less rich and less advanced can help. For this reason, I am hesitant to advance the ignition any more, especially until I see what my spark plug and other indicators about the jet tell me.

So, I think I'm good to get to the DMV and will use that ride to notice more about what's going on when I hear the four stroking. Happy to read about your experiences with this.
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