LCGB Forums

Hi All,

I'm starting to get out on my standard TV175 series 2 and was wondering what kind of performance to expect?

It pulls great from 1st-3rd and is very nippy. It however seems to struggle in 4th and almost goes slower than in 3rd? I'm not expecting the earth performance wise but trying to deduce whether it's just how it is or if there is something amiss... Quoted top speed is 56, so was hoping for 50 real world...

It felt a little lean so have gone up a couple of points on the main jet (still feels this way on the pilot so might go up a point there).

Spec as follows:
62.4mm piston.
60mm crank with 116 rod.
Electronic ignition.
Standard series 2 exhaust.
Standard series 2 TV carb, with scootopia 'free flow filter'.

The gearbox is too tall. It struggles to pull fourth. Probably your best bet is to fit an LI150 gearbox, to be honest. I'd also fit a S3 exhaust.

Not exactly "standard" is it?

Well it is more standard than most (and anything I've ever built previously...)

Other than an extra 5cc and a more modern ignition its pretty much as the factory intended.

I did think it could be 4th. Its final drive ratio of 4.8 which is similar to an Li150 with 16t sprocket. So maybe its a bit much for the old girl to pull.

It may be a case of modifying your riding style I had a TV 200 and that required holding it in 3rd and bring the revs right up before going into 4th and most town riding was done in 3rd

That's a perfect gearbox.

Check for blocked exhaust, retarded timing, binding rear brake, mixture too rich.
As suggested, make sure you rev it out.

Cheers for the replies.

Like I say not expecting the earth, but a solid 50 would be ideal for my needs with this scooter.

Timing set a static 17degrees. An Advance/retard unit might help it pick up a little quicker?

Exhaust is a brand new casa one so not coked up, however, I'm aware standard series 2 exhaust and intake is not the best. Maybe these can be upgraded in the future, but it feels a lot of money to upgrade for what is almost standard replacements...

Anyone used one of these filters?

https://www.dellorto.co.uk/shop/dellort ... bly-ub-mb/

I have one, so it could be a quick way to help get a little more air flow?

17 degrees BTDC timing is way back from spec when it was 23 or 21.
I would start by retiming to 19 BTDC.

After that it's go on a diet and lose 8 stone !!
That's how much I have gained since I was a teenager.

[quote="NorthernJordan"]Cheers for the replies

Anyone used one of these filters?

https://www.dellorto.co.uk/shop/dellort ... bly-ub-mb/

I have one, so it could be a quick way to help get a little more air flow?[/quote
That’s for the Ld
Don’t think it would make any difference I’d imagine Jordan

CHRIS in MARGATE wrote:17 degrees BTDC timing is way back from spec when it was 23 or 21.
I would start by retiming to 19 BTDC.

After that it's go on a diet and lose 8 stone !!
That's how much I have gained since I was a teenager.

A very, very old mate built up from scratch his 200 Lambretta recently & based it all on his previous experience from the 70's.

Despite the PWK carb being "too big" @ 34 mm, we now have that fairly spot on by blanking off the power jet & dropping to a 32 pilot (belated thanks to CHRIS in MARGATE)

However, the timing is set @ 21 DBTDC but it really goes so well, with no sign of pre-ignition or running hot, even with the lightweight 'J' series flywheel. The plug is text book colour, too.

As ever, 'we' always use the higher octane fuel & good oil, but it makes you wonder whether we tend to retard the ignition a bit too readily & even a bit too much, especially if our machines are used predominantly in town.....

This may be totally unrelated, stupid or both but hey-ho. When using a standard carburettor (as in this case) does a longer-stroking engine take longer to do one revolution than a shorter rod? If so, is it reasonable to expect less power available to achieve a higher rev rate?

Stroke and rod length are unrelated, 57/107, 57/110 , 57/116 the piston moves 57mm in all cases the only thing that changes is the position of the piston relative to the base face of the casing.

Changes to stroke and rod length need to be taken in the round and the required packers / gaskets and port timing adjustments need to be carefully calculated to ensure the desired results.

I did approximately 150 miles over the weekend (all two up) and really put it through it's paces.

It's excellent through the lanes and really is nice to ride. No worrying about ripping exhaust off the barrel when going over rough roads and plenty of low down pull.

To pull 4th a long open road is definitely advantageous and at some points we were hitting a good 50mph +
However, that was definitely exception and not the rule. Any hint of an incline or a head breeze killed 4th. I'm beginning to think now I've got some decent miles on it the jetting is definitely a bit rich and there is scope to reduce. It felt very lean when first run, but I've often found that fresh builds richen up as components bed in.

rossclark wrote:Stroke and rod length are unrelated, 57/107, 57/110 , 57/116 the piston moves 57mm in all cases the only thing that changes is the position of the piston relative to the base face of the casing.

Changes to stroke and rod length need to be taken in the round and the required packers / gaskets and port timing adjustments need to be carefully calculated to ensure the desired results.

I was right! (It was stupid). Ignoring my incorrect terminology, does the question make any sense knowing that this chap doesn't have 57, but 60

No question is stupid.

And my typo in the earlier post doesn't alter the principle - stroke is 58mm as standard.

With a longer stroke the piston travels further but at a given RPM the time taken is the same from TDC to TDC again for each revolution. The piston speed is necessarily that bit higher but isn't a major factor.

Increasing the stroke will adjust the port timings and durations by a few degrees. You'll also gain a few cc. Will it make a great deal of difference to the power of the engine? Probably not.