LCGB Forums

Hi all.

If you are running the GT186 kit, I would be really keen to hear what set up you have (gearing, exhaust, etc.) and your thoughts on the performance of the kit including observations on fuel consumption, comfortable touring speeds, etc.

I hope you can help.

Many thanks.
H.

GT186, 60/110 crank, PHBH 30, Franspeed Race, Li150 16/46.

Pulls really well, will happily cruise at 65 with another 10+ on top for when you need it. With the race pipe it does like to be in the power band so tend to ride it higher up in the revs, but saying that it is more than rideable around town. I average about 10 miles to a litre on long runs.

Many thanks Burnside - valuable information.

I run one on a 60/110 28mm delly BGM clubman standard tv175 gearing. It's a good all rounder the only issue I've had is with the petals which are now doubled up. I have a twin tank conversion with a 150 mile range recon its 12-13 to the litre.

I've got a pretty basic Gt186 setup on a S2 li150 with a 25mm Dellorto, reprofiled head, double upper reeds and a clubman exhaust. The air inlet is a series 3 with the air scoop opened up. I think it has a 16 tooth front sprocket on a 150 gear set.

I have not given it a real thrashing yet but it whips up to 55 mph pretty rapidly despite my 15 stone and has loads of bottom end grunt. There is a distinct powerband which starts at about 3500 rpm. No idea where it ends yet!

It feels like it will do about 65+.

BGM Clubman, 30mm PHBH, Li150 box 16/46. Crank wise, I have a Yamaha 115 rod on Indian GP 200 webs.

The one time I monitored fuel consumption on a trip to Kelso, I think, it was 13 or 14 miles to the litre.

I don't have anything negative to say about this kit ( I have not encountered issues with the reeds - yet). It's very smooth, very torquey, accelerates readily through the gears and is a joy to ride. Pistons, rings, reeds are all generic and pretty easy to get hold of.

After the Swiss Euro, on which I lost my tailpipe, I did my level best to blow it up on the way back from Dover. From my rev counter, I knew I was around 70mph on a Series 2 (with a tent, tools, spares etc) for large parts of the journey to the North West. It never missed a beat.

I've also doubled up my reeds. Not had any Reed issues with the 186 but did have a reed petal break on my GT200 so doubled them all up. Looks as though my economy is worse than most but I am running slightly rich, will get it on a dyno at some point!

Hi all.

A good number of positive comments and welcomed advice about petals. Fuel economy seems reasonable too.

Thank you for your contributions.

H.

why exactly do people double up on the reeds?

Doubling up the top reeds is recommended by Rich T on the 186 if using an expansion exhaust due to the low "blow down"

By top reeds do you mean the ones nearest the cylinder head?
I didnt know it was recommended have to admit

Donnie wrote:By top reeds do you mean the ones nearest the cylinder head?
I didnt know it was recommended have to admit

The reeds above the boost port. I only found out myself after the kit was already fitted when reading a thread either on here or on scooptopia. The reeds can suffer more if using an expansion and the easy solution is to double up the reeds, but raised the exhaust port a little can also help.

ah, mines a second hand kit and the previous owner had had the exhaust port raised a bit already so might be ok plus mines got a third port in the casing behind the reed block

Showing my extreme ignorance of the dark arts of tuning I know but what do you do to raise the exhaust port?
Is it simply opening up the top of the port a bit with a dremmell?

Marty ULC wrote:Showing my extreme ignorance of the dark arts of tuning I know but what do you do to raise the exhaust port?
Is it simply opening up the top of the port a bit with a dremmell?

When i had mine richard taylor recomended raising the exhaust port by 1mm. Yes i dont see why you couldnt do it with a dremel with decent cutter installed.

I am currently building a GT 186 engine running a 60mm crank, 28 phbh and an LI 150 box with probably 16 46 gearing. I want to keep a standard look so wondered if anyone was using a Gori exhaust and what difference is there between a Gori and the BGM Clubman ?

I'm going to stick my neck out a little here..And my kit may have been a complete one off?
Initially I had a 'dodgy' GT186 kit/porcupine head - but it's sorted now

Here's the story..

From a couple of years ago..
Have a GT186/porcupine head/BGM Exhaust big bore V2/25mil dellorto/SX200 stock gearing/58 MEC crank - all setup as per the book - squish correct etc.
Ran it in, again as per the book and noticed it would backfire when going onto reserve. So bad it took out a set of reeds on one occasion!!
Contacted Richard who was extremely helpful in suggestions, but we never solved the mystery back fire
Got it dyno'd after run in - 10BHP!!...disappointed after spending north of £1K would be an understatement
Went to the little Brittany rally a few days later and got left behind by everything - even a standard P2

Returning from Brittany something had to be done so I contacted Chris Sturgess who was at the time was mentioned in a scootering article about GT kits

Chris worked some magic on the kit, but crucially found (along with Adam, who also told me what was wrong prior to the kit going to Chris) that the compression was way way to low.
Anyway long story short - same setup as before produces 18BHP and now no backfire

I've now installed a Cyclone which has improved things further removing the SX200 3rd to 4th step in gearing
This wasn't a huge problem so don't let a SX200 box put you off

I wouldn't mind changing the BGM big box for a Rimini Gori GP50 - however the Cyclone has wiped me out a little financially for a couple of months. Although I don't regret getting the cyclone in anyway.

Hope this helps in some way - but, maybe not

nsaints wrote:I'm going to stick my neck out a little here..And my kit may have been a complete one off?
Initially I had a 'dodgy' GT186 kit/porcupine head - but it's sorted now

Here's the story..

From a couple of years ago..
Have a GT186/porcupine head/BGM Exhaust big bore V2/25mil dellorto/SX200 stock gearing/58 MEC crank - all setup as per the book - squish correct etc.
Ran it in, again as per the book and noticed it would backfire when going onto reserve. So bad it took out a set of reeds on one occasion!!
Contacted Richard who was extremely helpful in suggestions, but we never solved the mystery back fire
Got it dyno'd after run in - 10BHP!!...disappointed after spending north of £1K would be an understatement
Went to the little Brittany rally a few days later and got left behind by everything - even a standard P2

Returning from Brittany something had to be done so I contacted Chris Sturgess who was at the time was mentioned in a scootering article about GT kits

Chris worked some magic on the kit, but crucially found (along with Adam, who also told me what was wrong prior to the kit going to Chris) that the compression was way way to low.
Anyway long story short - same setup as before produces 18BHP and now no backfire

I've now installed a Cyclone which has improved things further removing the SX200 3rd to 4th step in gearing
This wasn't a huge problem so don't let a SX200 box put you off

I wouldn't mind changing the BGM big box for a Rimini Gori GP50 - however the Cyclone has wiped me out a little financially for a couple of months. Although I don't regret getting the cyclone in anyway.

Hope this helps in some way - but, maybe not

There have been a lot of reports that the centre plug blank was loose and this would cause loss of compression.

Understood.
This was however the volume of the cylinder head bowl being to large. The head was taken by Chris to Darrell Taylor and reprofilled

Do you remember carb jetting? (25 PHBL) Is it with remote filter?
Plus any idea what was the combustion chamber volume of the porcupine head?
I'll play with a similar set up and I'm never lucky
Cheers.