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I’m thinking should change my crank on my GT186. The existing crank is TV175 as far as I can tell and although it was rebuilt (as the engine was by a previous owner) by Harry at Pro Porting, so doubtless done well, I’m nervous that it’s not a GP tapered crank from what I’ve read (although I am running a Varitronic so the flywheel is lighter). It also means I’ve got a stack of base packers because of the long con rod.

What would be a good recommended crank and bearings to buy? I’ve seen the GT ones but they’re pretty pricey and I’ll also have to buy a replacement flywheel so I’m trying to watch the costs a bit. Is there something that would do as well that’s a bit less doshy or should I bite the bullet? And while I’m at it, is there any great benefit to fitting a 60mm rather than a 58mm.

It’s the first time I’ve done a crank change so don’t want too many obstacles!

If you change the crank,you'll have to change the flywheel because you've changed to GP taper.

I bought a GP Tameni crankshaft with a 60mm stroke and standard 107mm length con rod when I rebuilt my GT186 engine two years ago. The GT manual has some good info about barrel heights and port timings and I chose that setup because it would result in a deck height of 0.2mm, as opposed to 1.2mm with the standard 58mm stroke. You can view the manual on-line here,

https://lambretta-images.com/granturismo-manual/12-suggested-specifications/

(I think the measurements for the three columns to the right relate to a 110mm con rod, rather than 107mm.)

I then had a 150cc cylinder head modified by Readspeed for the piston profile and also to give me a squish of 1.3mm without having to use cylinder head gaskets, base packers etc. I did need to grind out the crankcase a little so that the crankshaft/con rod didn't rub.

You will need a GP flywheel and stator plate if you are going to change to a GP crank. I bought SKF bearings which are fine in an engine of this spec.

Happy tinkering!

Thanks for the info fellas...

I was hoping to not get too involved at this stage with anything other than changing the crank and also the flywheel, head reprofiling and such are a bit beyond my grasp at the moment. One thing for the GT crank is that I believe it should fit without further modification?

Regarding the flywheel, it is a Varitronic system and whilst I realise I would need to change the flywheel, would I also need to change the stator?

Hughieboy wrote:Thanks for the info fellas...

I was hoping to not get too involved at this stage with anything other than changing the crank and also the flywheel, head reprofiling and such are a bit beyond my grasp at the moment. One thing for the GT crank is that I believe it should fit without further modification?

You shouldn't need to do anything with your head other than play with gaskets to get the squish right. As regards the crank, I have just purchased a GT200 kit complete with a GT 60 x 110 crank. The kit has only covered 400 miles and I dont need the crank as I already have one in the engine the kit is destined for. PM me if you are interested

Colin

If it's a TV crank it will have a 116 rod. If porting work has been done, it will be to match the 116 rod. I'd suggest you strip it down and check the rod/barrel before buying a new crank.

MickYork wrote:If it's a TV crank it will have a 116 rod. If porting work has been done, it will be to match the 116 rod. I'd suggest you strip it down and check the rod/barrel before buying a new crank.

No porting work has been done on the barrel, I bought it brand new and fitted it with packers to get the right height. RT said it should be ok port timing wise as long is it was a 58mm crank (which it is). I will just be changing the crank to something that suits it better strength wise potentially. It runs ok, I’m just nervous of coming unstuck with the existing crank and bearings as they are few years old now and obviously have an Li taper. It gives me some confidence that folks who know a lot better than me on here have said that it may well be ok because I’m running a lighter flywheel but I would be gutted if it all went belly up just because I hadn’t beefed it up.

coaster wrote:

Hughieboy wrote:Thanks for the info fellas...

I was hoping to not get too involved at this stage with anything other than changing the crank and also the flywheel, head reprofiling and such are a bit beyond my grasp at the moment. One thing for the GT crank is that I believe it should fit without further modification?

You shouldn't need to do anything with your head other than play with gaskets to get the squish right. As regards the crank, I have just purchased a GT200 kit complete with a GT 60 x 110 crank. The kit has only covered 400 miles and I dont need the crank as I already have one in the engine the kit is destined for. PM me if you are interested

Colin

Pm sent.

Hughieboy wrote:

coaster wrote:

Hughieboy wrote:Thanks for the info fellas...

I was hoping to not get too involved at this stage with anything other than changing the crank and also the flywheel, head reprofiling and such are a bit beyond my grasp at the moment. One thing for the GT crank is that I believe it should fit without further modification?

You shouldn't need to do anything with your head other than play with gaskets to get the squish right. As regards the crank, I have just purchased a GT200 kit complete with a GT 60 x 110 crank. The kit has only covered 400 miles and I dont need the crank as I already have one in the engine the kit is destined for. PM me if you are interested

Colin

Pm sent.

Not seen anything

Not seen anything [/quote]

Thats odd.... just tried again!

Colin (coaster),

I have tried to pm you but for some reason it won't send, it's just sitting in my Outbox. I am interested in your crank, if you could maybe try and pm me through the site with details that may work? I may then be able to reply or you could send me your email address.

I've emailed admin about it but can't seem to do much else...

Hughieboy wrote:Colin (coaster),

I have tried to pm you but for some reason it won't send, it's just sitting in my Outbox. I am interested in your crank, if you could maybe try and pm me through the site with details that may work? I may then be able to reply or you could send me your email address.

I've emailed admin about it but can't seem to do much else...

Hi Hughie, your message came through at 10pm and I've just replied

Colin

It would be false economy to fit a new crank and not fit new main bearings and seals. ( You'll have to upgrade the mag bearing to a NU2205 anyway)

Harry Barlow uses the Koyo 8 ball main bearing on his builds.....

Wee Mark wrote:Harry Barlow uses the Koyo 8 ball main bearing on his builds.....

I'm a fan of these. Fitted one just last week.

Initially I wasn't sure if there was a particular part number for the Koyo with the extra ball, and after an extensive trawl of cyberspace left me none the wiser, I took a gamble, and purchased some Japanese-made 2RS types (from a reputable bearing supplier), and they turned out to be the 8 ball type. Don't know if I was lucky or if all Koyo 6305s have 8 balls.

Take a look at the SIP cranks if you're running a 116 rod.

Jordan

Ive got a brand new SIP 60x116 crank for sale if its of any interest?

Hughieboy wrote:I’m thinking should change my crank on my GT186. The existing crank is TV175 as far as I can tell

I'd have to question that as the piston in the 186 (and 200) is designed to work with the standard 58 x 107 crankshaft. The TV crankshaft is 58 x 116, so if you used a TV crank the piston would travel 9mm higher and poke out of the top of the cylinder. I'd suggest you measure the conrod before going any further.

corrado wrote:

Hughieboy wrote:I’m thinking should change my crank on my GT186. The existing crank is TV175 as far as I can tell

I'd have to question that as the piston in the 186 (and 200) is designed to work with the standard 58 x 107 crankshaft. The TV crankshaft is 58 x 116, so if you used a TV crank the piston would travel 9mm higher and poke out of the top of the cylinder. I'd suggest you measure the conrod before going any further.

Doesn’t the GT kit use the Suzuki piston with a 30mm crown height as opposed to the 39mm Lambretta Piston? So you’re 9mm will correct it’s self?