Vespa ET2 rebuild; low compression
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Member
Vespa et2 2004
Joined: 10 Jul 2019
Posts: 9
Location: Nevada
Wed Jul 10, 2019 6:45 pm quote
greetings; new to the forum and desparately seeking help....

I just rebuilt my daughters 2004 Vespa ET2. New cylinder, gaskets, piston, rings, carburetor, oil pump belt, drive belt, brakes and brake cables and fuel tap (all plarts bought from scooterpartsco or scooterwest). I degreased everything as well; I DID not open up the crankcase

Compression is at 80 (per haynes manual and forum postings should be ~110?).

Engine will start if I prime it; runs for a few seconds and stops. I validated fuel tap works ie disconnected fuel line, used kick starter, fuel comes out of line.

Ive removed and reinstalled piston, rings, cylinder and head numerous times; no change.

I am truly stumped (I've rebuilt numerous automotive (MG) engines). What am i missing or what hidden thing am i Missing ??

Help truly appreciated

thanks
frank
Molto Verboso
63 GL 150, 05 Typhoon, 09 Beo 200
Joined: 20 Jan 2007
Posts: 1717
Location: Grand Pothole Rapids, Michigan
Wed Jul 10, 2019 8:40 pm quote
Gaskets are a one time use.....I would try to smooth out the cylinder ends with some 400 grit emory cloth, using a figure 8 patern, and use some thicker gaskets. I would try to find those aluminum gaskets, and ditch that o ring gasket on the head. Also, there is some high temp gasket stuff in a tube....
Just don't over tighten it.....Don't ask me why I know!
Hooked
GTS 250ie Super, Italjet Velocifero, Scarabeo 150, S50,ET4
Joined: 22 Nov 2016
Posts: 398
Location: Winston-Salem, NC
Thu Jul 11, 2019 6:55 am quote
What is your squish? https://www.youtube.com/watch?time_continue=410&v=ZUe0p0DqFCk What kit did you use? Did you do a leak down test?
Ossessionato
73 Rally, 74 Rally, 76 ET3, 80 P200, 63 Li125, 65 Li225 Silver Special, 86 Elite 80, 2015 HD Road Glide Special, 2011 Ural Tourist
Joined: 18 Jan 2012
Posts: 3258
Location: Oceanside/ SF
Thu Jul 11, 2019 9:18 am quote
What condition are your reed petals?
Member
Vespa et2 2004
Joined: 10 Jul 2019
Posts: 9
Location: Nevada
Thu Jul 11, 2019 12:23 pm quote
thanks much for the input

Gaskets: new cylinder to block gasket due in tomorrow; will also use thin layer of gasket goop; will also torque per spec

Squish: will measure once back together
Kit: Stock 50cc Cylinder Kit for Vespa ET2 from scooterpartsco
Leak down test: am not familiar with/did not do; any links you can point me to??

Reeds: they are flat and seat properly

Thanks again; I'll follow up saturday or sunday

frank
Hooked
BV 350
Joined: 22 Nov 2016
Posts: 400
Location: Nebraska
Thu Jul 11, 2019 2:09 pm quote
crank seals?
Probably can't rule out crank seals either. If they're leaking a bit, air is lost, and your compression will be low.

When you put on the new bits, did you check piston ring end gap and piston clearance in the cylinder? I know, new parts, but I am finding that less and less reliable.

Might want to put the head on a piece of glass and assure that the sealing surface is flat.

Sometimes rings take a little while to seat, too, so I'd run it for a few hours before I took a compression check.

If it'll start at all, compression probably is not the problem. If priming starts it, your are not getting gas through the carb. Need to look there.
Ossessionato
Joined: 22 Oct 2011
Posts: 3994
Location: Tega Cay, SC
Thu Jul 11, 2019 2:47 pm quote
Jimdig beat me to it on checking the ring gap. Use stock gaskets. not thicker ones unless you are setting up the squish. Once you get it running' the rings will seat within an half hour.
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Granturismo 218
Joined: 04 Feb 2013
Posts: 5538
Location: South Carolina
Fri Jul 12, 2019 7:41 am quote
Is the arrow on the piston pointing down?

It's a stock replacement cylinder kit. These are meant to be thrown on worn out daily drivers in busy shops, not dialed in like a liquid cooled Malossi Team 3 top end. If you have 80 lbs. of compression with a new cylinder kit, it's not squish or ring gap.
If you put the head gasket on, and there is still no compression, it might be a warped head, it might be the crankshaft seals.
What did the old top end look like when you took it off? Knowing how it failed might make it easier to figure out what could be wrong.
Hooked
GTS 250ie Super, Italjet Velocifero, Scarabeo 150, S50,ET4
Joined: 22 Nov 2016
Posts: 398
Location: Winston-Salem, NC
Sat Jul 13, 2019 9:38 am quote
What Motovista said.

A good way to test the crankshaft seals is a leak down test. Here is a pretty long Youtube video on it: https://www.youtube.com/watch?time_continue=15&v=x-Jarx2od6I. It may be long but it is complete.
Member
Vespa et2 2004
Joined: 10 Jul 2019
Posts: 9
Location: Nevada
Sat Jul 13, 2019 3:07 pm quote
greetings; thanks for all the posts; I used a little bit from each

It now starts, idles and runs fine up to ~20mph; then bogs down and will die if i open throttle more (it will also bog with no load (up on kickstand) if I open throttle to that point).

to get it started:
- new gaskets; cylinder and head (aluminum)
- new ignition coil (was already on order and came in w the gaskets)
- sanded (using glass surface) cylinder and head surfaces
- dinked with carb mount to intake (ie removed, re inserted, re tightened screw clamp

it took about 10minutes of turning over before it started up.

It now starts, idles and runs fine up to ~20mph; then bogs down and will die if i open throttle more (it will also bog with no load (up on kickstand) if I open throttle to that point).

NOte: I am running it with the air cleaner off (making the mix too rich???)

Bogging issue: i'm thinking its carb/air leak stuff; will investigate more tomorrow.

feedback appreciated on the bogging down over 20mph issue; everyones insight much appreciated

thanks
frank
Veni, Vidi, Posti
Neutrino MP3 492.7 AK, 2013 Moto Guzzi Norge
Joined: 29 Mar 2008
Posts: 21368
Location: Harriman, Tennessee, Tn
Sat Jul 13, 2019 3:39 pm quote
is the spark plug rich or lean?
Hooked
GTS 250ie Super, Italjet Velocifero, Scarabeo 150, S50,ET4
Joined: 22 Nov 2016
Posts: 398
Location: Winston-Salem, NC
Sat Jul 13, 2019 5:06 pm quote
With the air box off itís to lean and will bog. Too long and it will seize on you. Make sure the cooling shrouds are in as well.
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Granturismo 218
Joined: 04 Feb 2013
Posts: 5538
Location: South Carolina
Sun Jul 14, 2019 8:09 am quote
frankiep wrote:
NOte: I am running it with the air cleaner off (making the mix too rich???)


thanks
frank
This is the reason it's not running well. Too much air.
Member
Vespa et2 2004
Joined: 10 Jul 2019
Posts: 9
Location: Nevada
Sun Jul 14, 2019 1:38 pm quote
greetings
Installed airbox (carb restrictor in place); really no change in symptom; anything over 1/4 throttle causes a bog; full throttle engine dies. Up to the 1/4 throttle (~25mph) runs and accelerates great; idles nicely too.

Heres the testing I've done; with a total run time on engine rebuild of approx 40 minutes:
- varied mixture setting from 1/4 to 3 turns; performance and symptom appears to be the same across all mixture settings
- plug appears black/wet after runs at all mixture settings
- Throttle slide moves from idle position to full up at full throttle twist; needle stays in base of carb (not sure if that means anything?)
- compression test at end of ~40 min of testing remains ~80lbs

the only thought i'm capable of:
Could the autochoke be stuck on (brand new carburetor) ? What does the choke do when electrical cable unplugged; full off or full on?
I've not looked at carb needle setting; read the post in previous link; not clear to me whether I've got a 'too rich' situation or 'too lean' situation ??

Other trouble shooting i should try?

as usual, your feedback and experience much appreciated

thanks
frank
Member
Vespa ET4 Piaggio MP3 Vespa PX
Joined: 12 Jul 2019
Posts: 14
Location: New Brunswick GA
Sun Jul 14, 2019 2:00 pm quote
What carburetor are you using?
Member
Vespa et2 2004
Joined: 10 Jul 2019
Posts: 9
Location: Nevada
Sun Jul 14, 2019 3:19 pm quote
Thx; the carb is a direct replacement for the stock dell Orto

Frank
Hooked
BV 350
Joined: 22 Nov 2016
Posts: 400
Location: Nebraska
Sun Jul 14, 2019 4:38 pm quote
Check
Check that the float valve is shutting off (fuel level in float bowl correct).

Even with an unusually high float level, so long as the needle is in the needle jet (throttle closed) it'll run OK. As soon as the needle starts coming out of the needle jet it will flood the engine.
Member
Vespa ET4 Piaggio MP3 Vespa PX
Joined: 12 Jul 2019
Posts: 14
Location: New Brunswick GA
Sun Jul 14, 2019 8:31 pm quote
By direct replacement do you mean it is a DellOrto 12mm and it came complete with the electric choke and throttle cable?
Member
Vespa et2 2004
Joined: 10 Jul 2019
Posts: 9
Location: Nevada
Sun Jul 14, 2019 8:41 pm quote
Correct
Veni, Vidi, Posti
Neutrino MP3 492.7 AK, 2013 Moto Guzzi Norge
Joined: 29 Mar 2008
Posts: 21368
Location: Harriman, Tennessee, Tn
Mon Jul 15, 2019 10:22 am quote
frankiep wrote:
Thx; the carb is a direct replacement for the stock dell Orto

Frank
even though its a direct replacement did you change the main jets and needle settings?
Member
Vespa et2 2004
Joined: 10 Jul 2019
Posts: 9
Location: Nevada
Mon Jul 15, 2019 10:31 am quote
Thx; I did not check nor change any jets; just dinking w mixture settings via screw

Thx
Frank
Member
Vespa et2 2004
Joined: 10 Jul 2019
Posts: 9
Location: Nevada
Mon Jul 15, 2019 2:50 pm quote
greetings

My troubleshooting today revealed:
-once throttle is at 1/4, if I block 90% of the air box input (the input that comes up under the seat), the revs will pick up and continue to increase to wide open throttle (ie normal performance). If I block entire airbox input input the engine will die

So...:
- i removed carb, adjusted needle from top position down 2 notches (ie position 3; old carb set at position 2)

Reinstalled; SAME PROBLEM EXISTS. And again, if I block air intake past 1/4 throttle, revs increase up to wide open throttle.

Given that, it obviously (?) starts to run extremely lean past 1/4 throttle.

-Should I adjust the needle further towards rich
- Do I have a massive air leak ? (if I block air input, the engine will die)

Divine insight appreciated
thanks
frank
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Granturismo 218
Joined: 04 Feb 2013
Posts: 5538
Location: South Carolina
Mon Jul 15, 2019 10:30 pm quote
There was a plate with holes in the intake of the new carburetor. Did you leave it in? If not, you need to put it back in to make a stock ET2 run right.
Hooked
GTS 250ie Super, Italjet Velocifero, Scarabeo 150, S50,ET4
Joined: 22 Nov 2016
Posts: 398
Location: Winston-Salem, NC
Tue Jul 16, 2019 5:21 am quote
Based on your trouble shooting you are running Lean. Do what Motovista said and see where you are. The screw you keep adjusting just handles the idle circuit. Your problem is in the needle or main jet. But put the plate back in first.
Member
Vespa et2 2004
Joined: 10 Jul 2019
Posts: 9
Location: Nevada
Tue Jul 16, 2019 7:19 am quote
Thx; yes; the plate has been in place from the start

Frank
Hooked
2003 Vespa ET2
Joined: 05 Apr 2019
Posts: 134
Location: Cambridge, MA
Tue Jul 16, 2019 12:01 pm quote
I suspect you will need to raise the needle....in other words, move that clip one notch lower and report back

might be a too small main ..but try that needle a little richer to start
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