Converting Gori 175 to 185/190

[Martin s]

I've got a new Gori 175 kit on the shelf and have all the bits to build up a new engine.
I'm wondering if I could do something with the kit rather than the ok but a bit mundane
performance as standard. I already have a built up Gori 175. Got a 60/110 crank to use so would
any of the Suzuki/Wiseco 64/65mm pistons be suitable for this hopefully without topping and tailing?
I understand head may need to be reprofiled and perhaps ports looked at. Thinking of up to 25mm carb.
Cheers
Martin.

[Knowledge]

Interesting idea. This is the first time I have heard of someone trying to oversize a Gori kit. Go for it.

I think the Gori kit usually runs a 58/107 crank, so the extra stroke and conrod length will need to be taken into account when adjusting for the lower compression height of the TS185 piston. I could do the maths I guess, but not this close to bedtime. I will not rule-out the possibility that the barrel will need to be shortened.

One thing that I came across when fitting a Mugello 225 barrel was that the transfer timings were very low. I learnt that the 225 barrels were just bored-out 200 barrels. The angle that the transfers enter the barrel mean that as you increase the bore diameter, the transfer timings reduce.

Now this may not be an issue with the Gori barrel if the transfers enter the bore at right angle, but it is worth having a visual check of the Gori barrel to see if this might be a consideration. I mention this as it may be a consideration when shortening the barrel.

I would not necessarily jump straight in for an expensive piston: Mitaka pistons are good and very cost effective and Suzuki pistons are still available (I think I have a few in the workshop). I seem to recall that the TS185 ER pistons were the best, due to the position of the piston ring pegs.

[vegansydney]

I've never seen a Gori 175 in the flesh, but in regards to pistons, and as noted above, the TS185ER pistons (piston: 121100-29900 | rings: 12140-29010 | pin: 12151-60D00) are best for conversions as they have the top ring peg in a more suitable location and recesses around the gudgeon/wrist pin. You can still find them NOS for as little as $25, Suzuki still manufacture them, albeit in 0.50mm increments rather than 0.25mm, as do Wiseco, and others. Given the compression height my preference would be to fit either an RD400 rod or a TV rod.

Good luck and please keep this thread updated with your progress.

[Knowledge]

Wise words VS. The choice of conrod length will of course be critical as to whether the barrel needs to be top and tailed.

With this conversion on an OEM barrel or the Scooter Resto barrels has been keeping the inlet timing under control. It was too easy to end up with inlet timing of 160degrees when 145degrees should be considered the max. A longer conrod should help keep this under control.

You are going to need to take some measurements and perhaps make some allowance for ports which enter the barrel at an angle (inlet and transfer) if the bore is enlarged.

[hullygully]

Hi Martin s, I've a Gori 198, but as std it's already 'top & tailed', so tread carefull.
Mine, after an AF's & Mick Abbey tune, BGM clubman, Wossner piston & 26mm Delly, pulls like a train & gives any small block (& some large blocks) a run for their money

[Martin s]

Thanks for the great info from your replies. I will have a look at the transfer port angles as mentioned when I get chance. Purchased a 58x116 tameni crank from Italy for a very good price of £100 delivered so I'm hoping this will be more suitable for a Suzuki piston. It won't go wasted if not. To be honest I wanted to try a Gori 200 sport, but I was told they're not ideal for a rebore, so got another 175 which was fairly cheap. Searched out lots of pattern pistons under the 29900 code for not a great deal of money, are they as usable as say a Mitaka or wiseco piston?

[vegansydney]

Searched out lots of pattern pistons under the 29900 code for not a great deal of money, are they as usable as say a Mitaka or wiseco piston?

Unfortunately I can't help with you with that as I've been lucky enough to find NOS Suzuki ones for cheap. Given that a large number of 'Suzuki 190' conversions have been done over the years, hopefully someone will be able to give you an honest answer.

As a side note, I've noticed that AF Rayspeed are now selling a 64mm Wossner piston. When I emailed them several weeks ago about the compression height they told me it was designed for a 58/107 crank.

[Warkton Tornado No.1]

With the 60 x 110 crankshaft that you already possess, I think you have acme good options if you can get your head around certain criteria that there will be some prejudice against.

If you browse the (full USA) Wiseco catalogue, besides the excellent TS 185 piston, you will see Polaris Indy pistons commencing @ 65 mm.

They are excellent pistons IMHO, very 'Suzuki RM-esque') but have 18 mm gudgeon pin bores & only one ring. As per the RM but not Lambretta!

I am fully aware of some having issues with sleeving down the gudgeon pin bores, but I have used the flanged Glacier bushes for donkey's years without problems on road & track. Likewise the single ring, though if a motor is to do many road miles, I nowadays go to the nth degree to fit an air filter, which seriously cuts down wear & tear as well as saving much otherwise wasted fuel. I do this even to other people's road engines that come to me for rebuild.

Mine is just another opinion that you may choose to disregard. If the barrel looks capable of being bored to 65 mm, I can help you out with a cast piston with ring as I somehow received some in error when I ordered 1.0 mm oversize....

[GExS]

I have done quite a few Suzuki 185 conversions, always used 60X115 cranks with 1mm packer on the bottom of the barrel, no topping or tailing needed and getting to 20Occ's. The first one I used a TV 175 barrel, the other two I used SR 64mm barrels which are the best of both worlds IMO with an iron lining and alloy fins. Great conversions, using 22mm Dellorto or Jetex and STANDARD exhaust . Gearing closer to a final drive of 5.0 is better.
I have also tried a Gori 200 Sport, nice clean kit but I found the head will need to be reworked. I can not remember the size of their bores but Suzuki pistons start at 64mm. I was told early Suzuki pistons have the peg rings in the wrong place but when Mick Abbey lined a piston up with a SR barrel they were fine. Overall, a good idea to use a Gori barrel, even better if they are 64mm.

[Warkton Tornado No.1]

I have done quite a few Suzuki 185 conversions, always used 60X115 cranks with 1mm packer on the bottom of the barrel, no topping or tailing needed and getting to 20Occ's. The first one I used a TV 175 barrel, the other two I used SR 64mm barrels which are the best of both worlds IMO with an iron lining and alloy fins. Great conversions, using 22mm Dellorto or Jetex and STANDARD exhaust . Gearing closer to a final drive of 5.0 is better.
I have also tried a Gori 200 Sport, nice clean kit but I found the head will need to be reworked. I can not remember the size of their bores but Suzuki pistons start at 64mm. I was told early Suzuki pistons have the peg rings in the wrong place but when Mick Abbey lined a piston up with a SR barrel they were fine. Overall, a good idea to use a Gori barrel, even better if they are 64mm.

In general, I would agree with this advice, along with the well thought out suggestions already offered by other members....

I guess you are in danger of finding it difficult to make final choices

However, for cost, quality & living proof of suitability of pistons, you are unlikely to better the SR thin chrome ring piston or the TS185 if you wish to retain standard wrist pin diameter & the facility of two rings.

Whichever is selected will dictate the geometry of the finished engine, but I would personally always go for whatever increase in stroke & practicable longest rod length is convenient. Unless compromised to do so, I would suggest to stay beneath the 200 standard 66 mm bore.

Where I am likely to differ from others is that IMO lowering the primary compression is a good thing to do, but the increased rod length likely already gets you in the right direction!

In addition, if you must retain some kind of box exhaust, then that is going to be the hardest choice you can make, as I doubt any 'off the shelf' types are ideal for your set up, if any set up, as they have to be a compromise.

Only yesterday, whilst browsing an old article, I was reminded of just how advanced sprinters of the 60's were with their modified box exhausts! The Ancillotti brothers 'U' pipe to their gutted, standard looking box was HUGE but appears to have been tapered, just as all good expansion chambers are these days. The Ancillotti 'pipe may be extreme to what it is you, & many other home tuners, may wish to achieve or emulate, but it should surely be considered a significant factor toward the net result. After all, with the very basic tuning of the day in terms of components & knowledge, & with less than 250 cc, to achieve 110 mph with an estimated 28 BHP is still incredible to my mind, & you have to wonder whether the manufacturers of modern day box exhausts are somehow missing a trick......

[GExS]

Update; I got a 66mm Suzuki TE 185 piston (last size possible) and a Gori Sport 200 kit. The piston is too tight in the cylinder so it needs honing.
On another note the Gori kit has a few upgrades, copper head gasket and some holes drilled in side near the top to help with easier kicking off. Good job Gori!

[dscscotty]

just use a 66mm asso/mahle/wossnerm same compression height/dome height etc

[GExS]

just use a 66mm asso/mahle/wossnerm same compression height/dome height etc

Thanks but not for a 60x115 crank?