4t tuning thread

[richban]

latest carb mods no not yet. Will let you know after some proper testing this weekend. Plug has gone from full turn of colour on the base ring to 3/4 turn a little leaner full, throttle chop..

Well after the weekend racing and testing I have fixed the back firing of full throttle. As suspected, it was to lean on the needle. After a couple of needle changes everything came together. Still running a large jet 2mm. The main thing I learnt is before you go messing with the carb internals make sure the intake is not messing with your engine. Pod filter not enough volume, Trumpets no good to much length, open carb good. For my engine engine and carb that is. Airbox untested properly. The needle in at the mo is the one I started with! All the 3/4 throttle problems were intake related.

[richban]

Anyone trying to make a 4 stroke go fast?

I am thinking of going a bit mad on an FXR engine . Options are. Short stroke mega rev bomb or a long stroke torque monster. I like the idea of the stroking it up coz it may last longer (lower revs less stress??). Looking for 24rwh on the cheap can it be done??????????

[Kickaha]

Anyone trying to make a 4 stroke go fast?

I am thinking of going a bit mad on an FXR engine . Options are. Short stroke mega rev bomb or a long stroke torque monster. I like the idea of the stroking it up coz it may last longer (lower revs less stress??). Looking for 24rwh on the cheap can it be done??????????

If you go long stoke work out what your piston speed will be as it higher than a shorter stroke at the same revs

[richban]

If you go long stoke work out what your piston speed will be as it higher than a shorter stroke at the same revs

Does it matter? I am thinking this would be a short track engine. more torque through mid range.

[fi5hy]

buy a fuckin
Loncin rich and get it over with

[richban]

buy a fuckin
Loncin rich and get it over with

Not far from the truth. What I would end up with would be a 4 valve version of a loncin.

[speedpro]

Reports would indicate that a major fly-in-the-ointment is the sub-standard conrod. Why not just sort out a good one and tune from there. They seem like good engines apart from those rods which restrict the revs you can safely use. The man from Kelford cams will be able to help you going by Taupo at Christmas.

[gatch]

Anyone trying to make a 4 stroke go fast?

I am thinking of going a bit mad on an FXR engine . Options are. Short stroke mega rev bomb or a long stroke torque monster. I like the idea of the stroking it up coz it may last longer (lower revs less stress??). Looking for 24rwh on the cheap can it be done??????????

Problem too with a long stroke motor, if it is too long a stroke, the conrod will hit the bottom of the cylinder skirt.. Also your displacement will be way over if the bore stays the same. Though no doubt you know that.

I like the idea of a shorter stroke motor, BUt then you wold need a new barre as there wouldn't be enough meat to cut through to make much of a difference..

[richban]

Reports would indicate that a major fly-in-the-ointment is the sub-standard conrod. Why not just sort out a good one and tune from there. They seem like good engines apart from those rods which restrict the revs you can safely use. The man from Kelford cams will be able to help you going by Taupo at Christmas.

Yeh not sure if the rods are god or bad. When I can afford a new CDI I was planning to raise the limiter to 13500rpm. The engine I have at the mo makes power nicely to the limiter now. I am sure max hp is above that but I may be asking for trouble at the high revs. Mr Kelford is my bro. Very handy. He was very impressed with the buckets at Taupo. He has sold quite a few hot FXR cams down your way. We have been talking about doing something to the other engine for a while. Now I have the first edition working good, its time to start dreaming of version 2.

[Kickaha]

I like the idea of a shorter stroke motor, BUt then you would need a new barrel

Or a longer rod

[gatch]

Or a longer rod

Bigger bore barrel to get the displacement back to 150cc I should have said..

[richban]

Bigger bore barrel to get the displacement back to 150cc I should have said..

Nah re sleeve back to standard 60mm. Then stroked longer buy 1.5mm takes it two 156cc I think will have to check that. Then machine the top of the piston flat for compression. Well that was the plan a while ago. Also well its apart lighten the crank a little or a lot. Standard valves, better cams, same old carb setup. job done ish.

[gatch]

Nah re sleeve back to standard 60mm. Then stroked longer buy 1.5mm takes it two 156cc I think will have to check that. Then machine the top of the piston flat for compression. Well that was the plan a while ago. Also well its apart lighten the crank a little or a lot. Standard valves, better cams, same old carb setup. job done ish.

Put some knife edges on the crank..

I'm looking at buying a loncin later in the year. Will leave it standard for a while, then perhaps buy a second one and hotrod the shit out of it..

Cam, higher comp, port match, carb, MAYBE a short stroke project. Hell I'd stay working at my shitty workshop just to do it..

[Blackflagged]

Yeh not sure if the rods are god or bad. When I can afford a new CDI I was planning to raise the limiter to 13500rpm. The engine I have at the mo makes power nicely to the limiter now. I am sure max hp is above that but I may be asking for trouble at the high revs. Mr Kelford is my bro. Very handy. He was very impressed with the buckets at Taupo. He has sold quite a few hot FXR cams down your way. We have been talking about doing something to the other engine for a while. Now I have the first edition working good, its time to start dreaming of version 2.

Do the CDI`s come with an adjustable rev limiter? I think there unlimited(well most aftermarket) hence the rod problems.Anyone know of a cheap, say scooter aftermarket rev limiter?

[richban]

Do the CDI`s come with an adjustable rev limiter?

These do http://www.ignitech.cz/english/aindex.htm