LCGB Forums

I posted previously about my recently acquired 1962 TV 175 Series 3 and mentioned that I was experiencing some running difficulties with it.

A friend who is looking after it for me down in Cornwall i.e. riding it (! ) seems to think it may have been modified a bit. It has little low down/middle range torque but then goes well when been given the beans.

Not too bad on fairly level roads but in hilly Cornwall it gets to be a pain, especially as on one quite steep hill I struggled to get up it even in first gear if I let the revs drop. Not helped by the passage of time and being 3 stone heavier than in my yoof when I had my first one!

Also when I got it there wasn't an air filter fitted and when my mate fitted one it ruined the running; tickover was erratic and its performance was awful.

Anyway, if it has been modified I want to put it back to standard so that it pulls better at lower revs and makes it easier to ride and an air filter can be fitted again. So I shall be looking for a barrel, piston (as do not know if the existing is standard or bored at this stage) and maybe even a carb.

I don't want to skimp on quality so what are your recommendations for best suppliers? Are parts still available form Italy?

My friend fitted a 175 piston and barrel to his Li 150. His barrel was of Indian origin and he found problems with the threads not being at the right angle etc. He re-tapped them though and fitted the parts OK and it runs pretty well. Given his experience though I want to go for better quality.

Cheers, Chris

I'm no expert on the S3 TV175 but the barrel, piston and crank I believe are different to the 150s,200s in that the crank has a different stroke, piston is different because of the placement of the gudgeon pin (which relates to the crankshaft stroke) and the port timings on the barrel are matched to the piston. I am no engineer so can't explain very well. You'd be best looking at what you actually have eg a 150 barrel bored to 175 or an original barrel with matching crank. Then you will be able to look at the costings of what to fit/tune. I don't think it would be easy to use an original 175 crank on any after market kit but I could be wrong. Quite often just a change of exhaust and a modern carb can make a bit of difference so you could start there. Good luck and I'm sure more will be posted from others

I’m repeating myself here, to an extent, but presuming that the history is unknown, you should look thoroughly @ the bottom end. If you have a TV 175 crank, it would be unwise to fit a cylinder kit that gives any gain in torque & power.

Incidentally, the 58 mm stroke is identical to all Series III & GP but the rod is longer @ 116 mm as opposed to 107 mm.

That really ought to be your first port of call before considering any other upgrade to performance.

Once that assessment is done, & you know what’s required, then a kit would function well if married to upgraded components, specifically a good crankshaft with a decent big-end.

Personally, the long con-rod idea is something I would try & stick with & even try to use a crank with a longer stroke. They are obtainable these days in 60 mm, 61 mm & beyond.

Married up to a decent kit like a GT, Mugello or any of the others available for the small block, you should end up with an engine that will be a joy to ride, subject to the quality of the build. You might like to consider the pros & cons that any kit may offer. Reed valve engines can be really sweet in an engine intended to plonk around town on with the occasional run……

Based on my experience keeping a TV175 standard makes it a joy to ride.

Time warp to the halcien days of the 60's and 70's.

Thanks for the replies guys.

Yes, that's what I want to do, put it back to standard not modify it anymore (if it has been) to give it's rideability back rather than how it is now i.e. peaky. The performance of a standard TV 175 is fine for me, if I want performance I've got a number of motorbikes.

Just to give a bit of background I bought it last year off a neighbour of my friend in Cornwall whose husband had died some months earlier. He had rebuilt it after it had been flood damaged in the sixties, pretty much back to original. Bottom end is definitely TV 175 (verified by the club). What makes us think that it has been modified is how it suddenly takes off at high revs, more than my standard original one did. I doubt that this was done by the last owner though, maybe before the rebuild?

So as said, I want to investigate and price up a new standard barrel, piston and maybe a carb. and would appreciate where to get good quality items from.

If it's sluggish and only takes off at higher speeds, and particularly the business with the air hose, could possibly be something to do with the carb. Sounds like it might be over jetted maybe. Have you looked into that?

When I restored my TV3 last year the engine was standard but very tired.
I eventually found a standard 175 cylinder/piston etc kit from Beedspeed @ £112.

The inlet port was very very poorly shaped so I ground it out to blend to the gasket hole. This is typical of the Indian after market parts I think. The rest of it was great, on the scooter and runs well.

I had a TV3 in 69 and it certainly pulled up any hill though I was 10 stone then...
Rode to work a treat, lovely scooter in standard form.

Having ridden standard TV175’s I agree with the comments & think the plan you have now formulated to be very sound.

Effectively, ‘blueprinting’ what you have should transform your experience.

However, I would advocate certain minimum standards/parameters:

The crankshaft should have a good big end bearing in trying to keep the existing rod length which should be 116 mm.

If you feel little option to renewing your crankshaft, you’d be advised to use GP webs, but you may continue to utilise the longer rod & even your current flywheel if you change the centre.

Hopefully, @ worst you may need a rebore & piston. Think about the advantage of a piston with just two, thinner rings as well as the slight increase in capacity that may offer.

If your head/barrel cowling has no baffle to deflect air to the exhaust side, it is a wise modification.

Good Luck!

ToBoldlyGo wrote:If it's sluggish and only takes off at higher speeds, and particularly the business with the air hose, could possibly be something to do with the carb. Sounds like it might be over jetted maybe. Have you looked into that?

Yes, that was our thoughts and my mate had a look at the jetting when he tried fitting the air filter.

That was some months ago and I haven't spoken to him since about it. I'm going down to Cornwall (I'm in Warwickshire) at the end of February so I'll have a chat to him about it.

It wasn't used for a while before I got it so maybe it's just something as simple as a gummed up carb. affecting the slow running?

Anyway further investigation is required I think.

Thanks for the other replies as well.

Bit of progress.

My mate has found time to have a look at the TV. He's e-mailed me and says that he's cleaned the carb. and found that the pilot jet is on the small side and the main jet is on the large side when compared with standard.

He says he's not very impressed with the carb. anyway (but doesn't go into any detail) and is looking to replace that to see if that improves matters.

He does suspect though that the porting and hence the carburation has been messed with and that will be looked at if there is no great improvement after replacing the carb.

Timing is spot-on and there is a very good spark so at least that side of the equation is fine.

Only thing letting the looks down was a scrape and dent on the side panels due to at least one of them coming off. Those have gone to be repainted so that will be good.

Only a couple of weeks now before I go down and see him so will find out the latest.

More news.

Just spoke to my friend and he's been doing some more investigation. Big and little ends are fine but the piston (still standard bore) and inlet port have been messed with but not in a good way!

The port has been opened up and smoothed and the piston skirt filed. Trouble is whoever did it didn't know what they were doing! The result being that when the mixture is being fully compressed the port isn't covered properly. And the exhaust system gives virtually no back pressure. Fortunately amongst the parts that came with the scooter is a standard exhaust which is in good condition.

The piston and barrel are therefore scrap and my friend has already sourced a new piston, barrel and head etc. (what a fine chap) and a decent carb. which he has re-jetted to standard. So once that has been done it should go like a standard TV should and as well as it looks.

Going down in a couple of days so will be good to see what he's been up to.

All sorted now.

Thanks again for the detailed replies and suggestions.

Regards.