Fresh kitted Vespa S50 4T 4V won't start
Post Reply    Forum -> Project Reports
Author Message
Member
PX 125, S 50 4T
Joined: 01 Jun 2017
Posts: 13

Wed Jan 15, 2020 6:45 am quote
Hi everyone
before a few days I instal Big Bore Cylinder Kit (80ccm) by Malossi and alsow I instal Power Cam from same producer to my Vespa S50 4V 4T. I did it slowly ... no hurrying, each part of this "puzzle" was check before instal. Everything goes slightly, piston rings "clic" nice, tightening of all component on correct Nm, applycation of new bearing to camshaft was smooth ... and in my mind I telling "that will be nice tune up". After asembly I tryed to start engine. Rear wheel slowly spining and I could hear only starter but nothing more.
Starter works well, after a few attempts I smel gasoline so fuel supply should be OK too, carb is ok and all hoses are connected, spark plug is OK but dry. (should had be wet from gasoline after a few attempts to start???) What about ignition ... could it be that problem ?
Thanks for all opinions and replies.
Ossessionato
LXV 150 3v ie. Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 3425
Location: Kingdom of Lanna
Wed Jan 15, 2020 7:00 am quote
cam timing?
Member
PX 125, S 50 4T
Joined: 01 Jun 2017
Posts: 13

Wed Jan 15, 2020 11:16 am quote
In my opinion I did it correctly ... set center mark to the middle, chain were take down, ... etc .... before assembly I checked mark 4T on flywheel, put back the chain and check if is cam correctly moving with a few spins by flywheel.
Is it OK ?
Ossessionato
73 & 74 Rally, 76 ET3, 80 P200, 06 PX150, 61 Ser 2, 65 Silver Special, 86 & 96 Elite 80s, 2015 HD Road Glide Special, 2011 Ural Tourist
Joined: 18 Jan 2012
Posts: 3754
Location: Oceanside, CA
Wed Jan 15, 2020 1:14 pm quote
Iíd say Cam timing, fuel issue then spark.

Cam youíve addressed

Fuel issue- is the carb cleaned and is there fresh gas reaching the carb? Donít forget to upjet the main jet to compensate for the larger displacement.

Spark- you can test this by holding the bottom of the spark plug against a cylinder stud (ground) and cranking over the motor. It helps to have a friend kick over the motor so you can securely hold the spark plug/watch. Make sure to hold the rubber cap as you can get zapped
Ossessionato
LXV 150 3v ie. Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 3425
Location: Kingdom of Lanna
Wed Jan 15, 2020 4:45 pm quote
marten_px wrote:
In my opinion I did it correctly ... set center mark to the middle, chain were take down, ... etc .... before assembly I checked mark 4T on flywheel, put back the chain and check if is cam correctly moving with a few spins by flywheel.
Is it OK ?
Appologies but sometimes mistakes are made by well meaning people. Cranshaft could have been at the bottom of the stroke when the flywheel marks lined up. But if you are confident the piston was at top dead centre then we will have to look elsewhere.

Sparkplug car not fully secured?
Fueling can be isolated by spraying some cold start fluid into the air intake whn cranking. If it fires on that then is is the fuel system.
Ossessionato
LXV 150 3v ie. Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 3425
Location: Kingdom of Lanna
Wed Jan 15, 2020 11:00 pm quote
Off the top of my head bedcause i'm not stood next to the bike

Did you remove thlearnacese ce engine from the bike? Did you reconnect the grounding connection to the frame? maybe the plug is trying to spark but has not ground to go to.

Did you reset the valve clearances? New cam has higher lift and valves are not fully closing.
Member
PX 125, S 50 4T
Joined: 01 Jun 2017
Posts: 13

Thu Jan 16, 2020 2:22 am quote
MJRally wrote:
Iíd say Cam timing, fuel issue then spark.

Cam youíve addressed

Fuel issue- is the carb cleaned and is there fresh gas reaching the carb? Donít forget to upjet the main jet to compensate for the larger displacement.

Spark- you can test this by holding the bottom of the spark plug against a cylinder stud (ground) and cranking over the motor. It helps to have a friend kick over the motor so you can securely hold the spark plug/watch. Make sure to hold the rubber cap as you can get zapped
Carb were cleaned before a few weeks and gasoline is fresh. Jets are replaced too.
I try the spark plug.
Member
PX 125, S 50 4T
Joined: 01 Jun 2017
Posts: 13

Thu Jan 16, 2020 2:36 am quote
waspmike wrote:
marten_px wrote:
In my opinion I did it correctly ... set center mark to the middle, chain were take down, ... etc .... before assembly I checked mark 4T on flywheel, put back the chain and check if is cam correctly moving with a few spins by flywheel.
Is it OK ?
Appologies but sometimes mistakes are made by well meaning people. Cranshaft could have been at the bottom of the stroke when the flywheel marks lined up. But if you are confident the piston was at top dead centre then we will have to look elsewhere.

Sparkplug car not fully secured?
Fueling can be isolated by spraying some cold start fluid into the air intake whn cranking. If it fires on that then is is the fuel system.
Yes I put whole engine out and work with it separately...it's better then geting hands into small holes where is no free space.

OK ... I understand what you mean.
I have to disassemble it again and check all parts and setings.
I am patient and I like to learn some news ... but I should to consultwhole process with someone "who knows where and what to touch".
Member
PX 125, S 50 4T
Joined: 01 Jun 2017
Posts: 13

Thu Jan 16, 2020 2:03 pm quote
unfortunately ... it happened

will it be re-usable ?

IMG_20200116_201232.jpg

IMG_20200116_201216.jpg

Ossessionato
LXV 150 3v ie. Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 3425
Location: Kingdom of Lanna
Thu Jan 16, 2020 6:47 pm quote
Sure. It looks like you dodged a bullet. Have a really good look. That one valve only just touched and wiped a bit of carbon off. It also look like it did might not even have made a mark in the piston?
You need a thicker base gasket or a thicker head gasket. What do the instruction say?

Edit sorry had a brain fart yesterday
Member
PX 125, S 50 4T
Joined: 01 Jun 2017
Posts: 13

Sat Jan 18, 2020 1:36 am quote
waspmike wrote:
Sure. It looks like you dodged a bullet. Have a really good look. That one valve only just touched and wiped a bit of carbon off. It also look like it did might not even have made a mark in the piston?
You need a thicker base gasket or a thicker head gasket. What do the instruction say?

Edit sorry had a brain fart yesterday
In the piston are two small imprints "like from children teeth" ... nothing deep. As you wrote on one of exhaust valves is probably wiped a bit of carbon off. Isn't necessarily to clean head and valves?
There were packed three gaskets. I used two of them (green waxed paper and black I think this is metal sheet ). Green gasket has thickness 0.8 mm and I used as base gasket and black one has thickness 0.5 mm and that I use as gasket of head. In box was one more gasket (gray) it is widest it has 1.00 mm. But I'm not sure from which material is made.
May I have to use the gray gasket as replace for base (green) gasket ?
Instruction manual didn't talks about which gasket should be placed on base or between cylinder and head ... in fact there isn't mentioned anything about gasket at all. There is used word "assembling".
So what I should do now?

IMG_20200117_113525.jpg

IMG_20200117_113651.jpg

Ossessionato
LXV 150 3v ie. Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 3425
Location: Kingdom of Lanna
Sat Jan 18, 2020 3:00 am quote
Difficult doing this at arms length. Is the kit one that can be used for both two valve and 4 valve engines? Maybe the 4 valve engine requires the use of all the gaskets so tow at the bottom.

Edit OK found this
Quote:
WARNING !!! Into the kit you will fi nd two cylinder base gaskets with different thickness:
- 0,40 mm: to be used in 2 or 4-valve engines
- 0,80 mm: to be used in 3-valve engines
The piston with 3 valve housings is fully compatible with 2, 3 and 4-valve engines.
If your kit is Art. 3117771

http://storage.malossistore.com/files/montaggio/pdm/7317771.pdf




Arrow on piston is facing the exhaust/bottom of the engine. (sorry if this is an insult)

I can't find the instructions on line. (See edit above)

If you have the piston the correct way around and you still get interference then use both gaskets together at the bottom.

I'm running out of ideas.
Member
PX 125, S 50 4T
Joined: 01 Jun 2017
Posts: 13

Sat Jan 18, 2020 6:32 am quote
waspmike wrote:
Difficult doing this at arms length. Is the kit one that can be used for both two valve and 4 valve engines? Maybe the 4 valve engine requires the use of all the gaskets so tow at the bottom.

Edit OK found this
Quote:
WARNING !!! Into the kit you will fi nd two cylinder base gaskets with different thickness:
- 0,40 mm: to be used in 2 or 4-valve engines
- 0,80 mm: to be used in 3-valve engines
The piston with 3 valve housings is fully compatible with 2, 3 and 4-valve engines.
If your kit is Art. 3117771

http://storage.malossistore.com/files/montaggio/pdm/7317771.pdf

Arrow on piston is facing the exhaust/bottom of the engine. (sorry if this is an insult)

I can't find the instructions on line. (See edit above)

If you have the piston the correct way around and you still get interference then use both gaskets together at the bottom.

I'm running out of ideas.
I have this kit

https://www.sip-scootershop.com/en/products/racing+cylinder+malossi+79+cc+_m3113905

it's same kit only different product number.
Piston is instaled correctly. You can see arrow on the bottom at the first attachet picture.
OK I try to use at first only the thicker gasket and if it will looks still to low I add a second gasket and check how it looks.
What about carbon on head and valves .... should I have to clean it ?
Ossessionato
LXV 150 3v ie. Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 3425
Location: Kingdom of Lanna
Sat Jan 18, 2020 7:49 am quote
Technically you don't need tp remove the carbon deposits but it wouldn't hurt while it is apart.

Give it a soak in WD40 and use a scotchbrite pad. Bit messy but it doesn't have to be perfect.

Do you have a new sparkplug? If not you'll have to give that a good clean after the soaking process.

Wash off the cleaned surface before reassembly.

NB I think your kit has superceded the older one but it is difficult to tell. Same instructions should still apply.
Ossessionato
LXV 150 3v ie. Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 3425
Location: Kingdom of Lanna
Fri Jan 31, 2020 5:48 pm quote
Marten,

Whats happened?
Member
PX 125, S 50 4T
Joined: 01 Jun 2017
Posts: 13

Tue Feb 11, 2020 3:17 pm quote
waspmike wrote:
Marten,

Whats happened?
Hi waspmike ... sorry lot things to do in the job. At first I installed the thicker gasket. Next the head was cleaned and valves were set to the correct allow run-out 0.10 mm and when I assembled it I realized that on the first assembling I didn't correctly set a piston. I didn't think about it and set it into the top position (and that was wrong). Problem was on my side ... probably I was hurry. The correct position for asembling is 3mm before the top of cilinder and "4T" mark on the ventilator confirms it. So I put everything together and .... she lives !

Thanks for all replies in this thread !

IMG_20200129_225231.jpg

IMG_20200129_225043.jpg

Ossessionato
LXV 150 3v ie. Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 3425
Location: Kingdom of Lanna
Fri Feb 28, 2020 5:08 pm quote
Result.
Land of 10,000 Scoots Rally   Vespa Wasp Pin Badges   Scooter Parts Company
Post Reply    Forum -> Project Reports
[ Time: 0.1627s ][ Queries: 26 (0.0270s) ][ Debug on ]