Couple of Avanti TT3 questions

[RBG]

I'm just cleaning up some Indian 200cc engine casings prior to building my Avanti TT3.
I've yet to choose a crank the choice I have here in the US is in order of cheapest to most expensive

GP200 - Mec Eur - Race : 58 X 107MM
TAMENI GP CRANKSHAFT: 58 X 107MM
AF/RB RACE CRANKSHAFT: 58 X 107MM
AF/RB RACE CRANKSHAFT: 60 X 107MM
BGM CRANKSHAFT: 60 X 110MM

If I do go for a 60mm stroke by how much if at all do I need to trim the piston by
and is it worth paying the extra money for an AF or a BGM Crank as they work out about twice the price
of the cheeper Mec cranks....... The BGM's are pretty.

Is anybody running this kit through the Air Box to keep a standard look
if so how is it performing.

Still need to decide on a carb and I'm torn between the standard look
and Rons set up with a 30mm carb and a breath sweet filter and large tank

So Far I've got a ReedSpeed 5plate clutch and a LI 125 box.
Exhaust will be one of Ron's when he gets them.

Many Thanks
RBG.

[Minority]

Presume you are going to change the "standard " sprockets with your Li125 gearbox? Other wise the the final drive ratio will be very low for the Avanti kit.
Also, according to "Stickies", some 125 gearboxes may be too weak for a powerful engine (not sure what he classes as powerful though )

[RBG]

As with everything and anything to do with a Lambretta it may change, not fit or need fettling, if I was to win the pools
I'd splash out on a 5-speed box.
Late LI125 46 and 20 should give me a 4.23 final drive.

[mick1]

if your going that tall with a final drive I'd definitely have a 30mm carb.

I'm running a 4:6 g/box and a 28mm with a remote foam filter. Performs very well and quite economic to boot (50 mpg...ish).

I have a series 3 frame and hardly any clearance between the cylinder and frame. I put a shortened rear shocker (300mm) to help but still couldn't fir a PWK manifold on. If you go for a longer stroke be careful if the packer pushes the cylinder into the frame.

As with most of the questions about the Avanti....give Ron a call he's very helpful and always seems happy to talk about set-ups...

[coaster]

if your going that tall with a final drive I'd definitely have a 30mm carb.

I'm running a 4:6 g/box and a 28mm with a remote foam filter. Performs very well and quite economic to boot (50 mpg...ish).

I have a series 3 frame and hardly any clearance between the cylinder and frame. I put a shortened rear shocker (300mm) to help but still couldn't fir a PWK manifold on. If you go for a longer stroke be careful if the packer pushes the cylinder into the frame.

As with most of the questions about the Avanti....give Ron a call he's very helpful and always seems happy to talk about set-ups...

I agree about the carb size, I would think that anything small enough to run through the airbox would be too small to give any power

I have a 3mm packer and 300mm shock and have no clearance issues whatsoever on my Jet. I'm using a AF Inlet manifold.

[doggbhoy]

I have a 3mm packer and r1 rear shocker with no clearance issues...i use a 30mm phbh with breathe sweet filter it goes great but i wouldn't say it was economical

[Adam_Winstone]

I'd agree that the best thing would be to speak with Ron.

I'd also agree that 4.2 is too high a ratio and that you want to be looking at somewhere between 4.4 and 4.8, depending on what exhaust you are using, which is still a benefit over most other kits that would require a ratio between 4.6 and 5.2 depending on exhaust.

The only manifold clearance issues that I've had with the Avanti TT3 have been when experimenting with add-on reed manifolds (just to experiment but certainly not necessary or of any real benefit with this kit), which was also improved by fitting the shorter SIII length rear shock.

Stroke... I'd be tempted to stick to the standard 58mm stroke. My reason for saying this is that I've recently been offering up an Avanti TT3 to a casing with modifications to take a 62mm stroke crank and I don't really like the extended transfer timing that it results in. Whilst the 130 degree transfer timing is pretty standard for TS1 and Radido kits, both have been shown to benefit (for road use low rev torque) from a reduction in transfer timing, e.g. Taffspeed's fitting of 110mm rod, MB's machining down of base gasket face and fitting thick head gasket). Whilst a 60mm stroke crank would probably have given me a transfer duration that I would still have been happy with, having a few thousand miles of very happy Avanti TT3 riding under my belt makes me realise that I should stop messing about with the set up of this kit and simply use it in the 'off the shelf' configuration!

As far as standard 58mm stroke cranks are concerned... the only reason why my Avanti has been off the road for a while is because of a MASSIVE crank failure , which saw my MEC Race conrod break up at the back of the big end eye, exiting through the back of my casing as it went! I actually still rate MEC Race cranks as a good option for most road motors, tuned or not, and had done thousands of miles on this one before it went BANG! My first choice for road motors, after decades of reliable high power motor use, is a pair of SIL webs fitted with good quality and upgraded conrod and bearing, as per the AF upgraded SIL cranks. As the Avanti kit already has the port timings right for use with the standard 107mm long rod, I don't see any real benefit from going for the 110mm rod, which kits with too much transfer timing (IMO for fast road use) tend to suffer from.

All of the above are my opinion only and others will differ... but the first statement of 'speak to Ron' holds true.

Enjoy the kit.

Adam

[coaster]

......which saw my MEC Race conrod break up at the back of the big end eye, exiting through the back of my casing as it went! As the Avanti kit already has the port timings right for use with the standard 107mm long rod, I don't see any real benefit from going for the 110mm rod, which kits with too much transfer timing (IMO for fast road use) tend to suffer from

Qite nervous at picking you up on a point Adam as you are my guru :fb: However, (and please correct me if I have it wrong) but I thought the idea of a 110mm rod on a 58mm strike crank was that it gave a kinder angle to the conrod resulting in less side loading on the piston and less load on the small and big ends. I'm not sure HOW much benifit there is to be gained though.

cheers

colin

[Adam_Winstone]

Hi Colin,

Guru! You must be thinking of someone else, or have very low standards! (lol)

You are correct that the longer rod does help with side loadings and vibration, regardless of stroke, but not to the point that I'd be bothered to address it on a 58mm stroke... unless I wanted to unnecessarily tinker with motors (hey, that IS me!). There are those on here that will also tell you that there is a benefit to be gained by pushing the piston up the bore, so reducing primary compression and allowing more volume for incoming mixture, which some would argue with and others would agree with.

However, when you start to increase stroke then the piston gains travel at TDC and BDC so you would have to watch out for the piston skirt hitting the casing mouth at BDC, which I think some may have found when trying to fit 60mm stroke cranks with the standard Avanti piston [excellent piston ], so in these cases the longer 110mm rod would resolve this nicely. Indeed, the longer stroke gets then the longer a rod you need to consider. You will often find the ideal relationship of rod and stroke as 2x stroke, so there is no surprise to find that the recommended rod length for a 58mm stroke motor would be 116mm, being exactly what the TV175 III uses. However, the dropping of the 116mm rod for the 200cc Innocenti models shows that there are plenty of good exceptions to the rule... including many Jap configurations. The standard Avanti configuration on 107mm rod @ 58mm stroke is no different to the standard TS1 configuration, which has proven itself as reliable for thousands of motors so there really isn't any need to think of this as a failing of either kit. However, WE (the Lambretta massive) love to mess about with motor configurations and both Tino and MB have both produced 70mm pistons with the TV175 compression height for use with 116mm rods in TS1/Monza engines.

So... yes there are some benefits to be had but are they worth the additional work/modification when the standard 58mm/107mm configuration has proven istelf as reliable and capable of delivering high performance?... I think not in most instances unless the kit was specifically made for a different configuration. The 'off the shelf' Avanti TT3 really doesn't need any mucking about with and should be considered as a bolt on kit.

Adam

[coaster]

Thanks Adam , I can buy that, my path to lambretta enlightenment has taken a step forward

PS, you are way too modest