GT big block experiance : New GT crank info added

[hendy]

And just for clarity, i have never used any electrex gear on a lambretta so I'm not saying they're reliable.

Only that I've used electrex kit on other bikes without fault. Bmw, aprilia, bsa, Honda, kawasaki and maybe more, but never lambretta.

Just covering my arse in case someone feels like suing.

[Davidsquaredson]

The center plug blank, did you lock-tite it place? Just use washers off a spark plug? WHat torque did you tighten to?

THanks
David


just examined. I could almost remove with my fingers. signs of leak. I had a ring type heat pick up for tbe sensor at tbe base. is this also part of tbe problem?

[Rich_T]

I use a drop of silicone sealant on the blanking plug threads then tighten it up.

There is a 1/8" thread in the blanking plug specifically designed for K type probes (most commonly used on EGT gauges). There is limited space for ring type probes under the plug on Porcupine heads and it also creates a step in the combustion chamber,

[Davidsquaredson]

thanks. ring gone. a bit of high temp sealant on.

Sent from my HTC One using Tapatalk

[Grumpy225]

I use a drop of silicone sealant on the blanking plug threads then tighten it up.

There is a 1/8" thread in the blanking plug specifically designed for K type probes (most commonly used on EGT gauges). There is limited space for ring type probes under the plug on Porcupine heads and it also creates a step in the combustion chamber,

I was just wondering about that step problem. Figured I would need to cut the blanking plug to fit a copper crush washer to keep everything lined up.

[eden]

on the ones I do I take it into account when reprofiling the head for the increased cc then cut the red plug so it sits flush. Ive not yet had one come loose with the sensor under it though!

[kejj]

Hi
Here comes my GT200 Big block experience.
The engine was built during last winter/spring. It was back in to the bike by May-June. Since then I have done approx. 1000km during the summer. So here are my experience with the kit.
This was the first time I run an engine with reed fuel induction, I've been used to piston controlled fuel inlett.
I ordered the GT 200 kit from Rich. Top service.

The engine.
This was a SIL200 engine I've used for over 10 000km. Bought new back in 2007 and never touched a thing within the engine. Guess I was one of the lucky ones to get one that lasted for so long.
The last year it started to act up and upon inspection I found that the sil crank was misaligned. This left me with a 200 engine to try the GT 200 on! Perfect!

First, the ignition was upgraded to BMG stator with full wassel battery DC. Paired with a BGM CDI (died in august, Mitsubi one in now). SIL lightened flywheel on 17°.
I also did instal Rich T's prototype GT Cranks. The ones with SIL webs, Japan 110 rod and plastic stuffers with 58 stroke.
Indian GP gearing with final ratio at 5,22.
The carburetor is a PHBH 28 Dellorto with jetting according to the GT manual. After reading through this thread and the Scootering article I upped the main jet to 135. The PHBH breathes through a standard GP rubber below and a Ram air foam filter with some filter oil on. This way I recon I could run the carb with no filter if I wanted to with only a main jet upping to 140.
AV268 atomizer, X13 2nd clip needle, 40 slide, 55 idle jet, 70 choke jet.

For exhaust I choose the MBGM big bore V2. Sounds awfully loud but it does it's job and performs like an expansion.

I did polish up the exhaust port and matched the transfers to the casing.

The experience.
The kit with the phbh setup and the MBGM exhaust gives a clear power band. It starts to kick in at 4600RPM and revs on to 7000. keeping it within this range I can easily go through the gears and maintain speed and acceleration.

Anything bellow this revs and the scoot feels kinda, tired and hesitant to pick up. As soon as it reaches 4500 inch RPM it flies off like it's been kicked away! Turbo powers
Makes me happy with a smile. slow riding in traffic to work and it just feels a little bit hard on the low revs plus it drinks a lot of fuel. It needs revs and speed. I have calculated an average consumption of 0,76 l per 10 km.

I could go down on jetting on the range 1/4 to 3/4 range, to sort out the low revs running but the jetting is perfect when the engine is in the correct rev range so I'll keep it for now. Maybe either drop the needle one clip or change to X7 and do plug chops to see what happens.

One other thing I've noticed, when the revs reach the rate at which power kicks in it always makes a short hesitations before it kicks of. Something like the engine goes, yes, no, yes, on, yeeeeeeeeeees and off. This regardless of throttle position. It connected to the revs. I guess it's down to the boysen ports start to kick in.

a month ago I did a 400km trip 2 up. The bike worked prefect, never any trouble to overtake cars or climb hills. It pulled really well and acceleration was just a twist away.

Overall I'm very happy with the kit, would gladly recommend it to others. Also working with Iron means this kit probably gona survive a long time.

[eden]

Kejj your jetting does sound rich. I would definitely drop the needle to top clip position.

I've got back from Venlo yesterday and while over there I rode with a P200E which while 2 up was topping out at around 60mph so we rode most of the way sitting between 55 and 60... first fill up over there after doing 61 miles I was amazed to have only used 5.4 litres of fuel.
Now compare that to the first fill up back in the UK after doing 55 miles from Hull with a blowing exhaust stub riding with the choke on to compensate for the lean running due to the leaky stub riding with Sticky and co at between 65 and 73 it used 8.5 litres lol.

My conclusion was that even though the stub was blowing and letting air in making my tick over 700 rpm higher than normal, it wasn't running lean enough to warrent keeping the choke on so the rest of the way I didn't use the choke and it was fine.

[kejj]

Yes Eden, I will try the needle on top position.
Next thing I want to do is change the front sprocket to 19. This because right now I need to scream 2nd gear to run 50km/h which is a normal town speed around here. Either that or low revving 3rd with no punch in it.

[eden]

you might find it pulls better in 3rd with the needle dropped