LCGB Forums

This is my first G P, its unrestored original Italian 200 dl.that vibrates badly at low revs.

It starts o.k. and when warmed up will tick over on the stand but its not comfortable to ride.

To find the cause of the vibration i changed one part at a time, but nothing made any difference.

Changed engine mounts.
Changed small end bearing and pin.
Fitted new Italian barrel and piston.
Fitted new M B crank bearings and seals.
Chain tension is correct.
Fitted new red tip float needle in carb.( had early problems with flooding.)

Any advice please.

Where is the vibration felt? Could it be that the forks are loose and that this is shake that is coming through the bars?

Engine bolt done up too tight? Wrong engine cones?

I'll probably come up with a few more... none of which are likely to help but I'll come up with ideas.

Good luck.

Adam

If your scooter is unrestored is the ignition giving a misfire or has the timing moved. This could give a feeling like vibration. I have recently bought a GP 150 after 40 years since having a series 1 150 and I notice that has a certain amount of vibration. Other owners say that the GP has got some vibration. Would like to try someones GP to compare with mine.

ive a GP200 and had a few vibration issues over the years......

like adam advised is the vibes coming through the handlebars ?
if so you can focus on the headset and forks to see whats loose

another one i found was to take off the toolbox door to see if that cures it
as i had a worn lock i eventually found out through this ploy

also make sure that your petrol tap is not vibrating against your carb
it took me ages to track this one down as i thought it was in the handlebars at first
only with the panels off and reving the engine did i see that the long petrol tap
although well clear at rest started vibrating like mad once the revs came on
and rattled up badly against the back of the carb due to a worn front rubber

my final one was the flywheel this took a while to track down as well
i eventually found out that if i held the flywheel by the fins i could move
the whole unit up and down vertically by a mm so this ended up with me
getting a new crank to sove that problem

ive also had the seat vibrate badly as well so check that out

some stuff to go on as a starter for you

good luck!

You say this is your first GP.Is it your first Lambretta ? Have you ridden Vespas before this ? If the answer is yes to these questions,then thats the answer,Lambretta's vibrate.

Is the crank running out of true? (Twisted) Have you had it checked?,

put the scooter on the stand from the tool rool and check if there is any rocking sideways movement
of the back wheel if there is then theres a good chance your gearbox endplate may be loose
as over time the kickstart ramp on the endplate can work the gearbox endplate loose

dscscotty wrote:Is the crank running out of true? (Twisted) Have you had it checked?,

As above. If it is a knocking type of sensation then something is loose, severe vibration is generally crank related.

is this happening on the stand or in riding ? does it increase as the revs rise?you would need to isolate engine issues from frame/wheels problems i.e bearings and buckled wheels.

Thankyou for your replys and advice.

The vibration is felt through the seat and handle bars.

When warmed up and on the stand at tickover it vibrates normaly,but you dont have to open the throttle very far before it vibrates badly.
It vibrates at the same revs when ridden through the gears, it feels like i need to velcro myself to the seat.

Took it for first ride since fitting new crank barrel piston bearings seals and engine mounts,8 miles around town lots of stop and starts in traffic and the vibration was the same.

Have checked forks rear hub flywheel all ok.

Will check timing and other recomends and post outcome.

I do have other Lambrettas a series1 and series2's smooth, beautiful, lovely to ride. never had a (ssh.) vespa

Usually it would be the crank out of balance to cause such a discomfort?
Is it worth asking the supplier of the crank this question?

why not state the area you are from and ask if you can take it to someone 'in the know' by the time you have checked every thing out it may turn out to be something silly that you have not experienced! and yes we will all have done this in years gone by!

Have you tried a different flywheel on it?

My moneys on Crank!, ideally needs to be checked on jig or v blocks however if its really bad you can sometimes check it this way. take off your fan cowl and flywheel dust cover, take out plug and get some one to turn engine over slowly and look at the centre of crank, if it oscillates then its running out of true. Not the most technical method but worth a check.

Cheers
Scotty-DSC

Totally possible with a split crank like the 'Bretta's.
If this is the case will it have taken the crank bearings with it? (adding to the problem)

Did the fresh engine vibrate right from the start-up?

Sorry if this is obvious, but all the cooling fins are there?

bad vibration on my gp was caused by lack of good rubber washers between rear footboards and frame especially where they fasten to the bridge piece.i also felt that the bridge was a bad fit and felt it was being strained to tighten up.at a certain rev range it vibrates through the headset,increase the revs it stops then does the same again when you change gear.also felt through the seat.hopefully its may be something simple like this,easily checked and nothing lost if its wrong.

Exhaust downpipe or box resonating against the bodywork or frame ?

hi

thanks for all your replies.

its been a while, i had an operation on my shoulder so been out of action for 6 months.

since my last post.

i have shimmed the rear sprocket so it lines with the front, fitted new chain because the old one was stretched to its maximum.

i changed one of the clutch steels cos it had a piece missing.

took the front hub off and fitted new bearings, seals and spindle the original one had a 4mm bend on one end.

stripped the forks and rebuilt them.

changed the engine mounts again. fitted bgm ones with new cones and spindle.

on a positive note the scoot now runs without vibrating.

its really smooth to ride now.

for anyone following this post.

i brought the scoot untried from an LCGB member so i was unaware of the vibration but was told quote ( it has a bit of piston slap )

so i set off in the wrong direction by removing piston, barrel, crank etc etc.

what i have done to the scoot in the last 15 months has improved the running but the main cause of the vibration was the engine mounts.

thanks for all your advice i hope someone can learn from my mistakes.

regards phil

Good to know. My newly acquired dl150 vibrates also. It's just gone through a top end rebuild so thought it might be that but after reading this I will check all above.

Cheers
Kris