Tyz Carb Settings

[izzywithus]

Hi all, some more help please. I have removed the auto oiler from my TYZ Scottish and it is now running a bit rough.

Idle to quater throttle is fine but it will not rev out. Can anybody let me have the base settings for this bike? It has a JK carb running on full synthetic Castrol at 50:1.

Why would the carb settings be so far off after the removal of the auto oiler?

Thanks

Iain

[feetupfun]

Reason 1 If you didn't block the injection nipples, there will be air leaking in through them

Reason 2 Adding oil to petrol changes the viscosity (which is affects the way it flows through jets)

Reason 3 Adding oil to petrol changes the oxygen demand of the fuel

The biggest effect by far of these three would be Reason 1

[woody]

If I remember rightly when the autolube was removed from the old twinshock models, the carbs needed jetting changes (maybe just the main jet) as going to pre-mix alters the petrol/air mix, as per reason 3 above.

If I can find my TYZ manual I'll look up the jetting and you can compare to your carb

Edited February 10, 2010 by Woody

[izzywithus]

Reason 1 If you didn't block the injection nipples, there will be air leaking in through them

Reason 2 Adding oil to petrol changes the viscosity (which is affects the way it flows through jets)

Reason 3 Adding oil to petrol changes the oxygen demand of the fuel

The biggest effect by far of these three would be Reason 1

Hi Feetupfun thanks for the reply.

I am sure I got #1 right I also checked for leaks around the rubber boots and could find nothing.

#2 I guess this makes the fuel travel slower through the jets and therefore more air? So the mix is leaner?

#3 Does this mean the mix needs more air? So the mix is richer?

As you can see I don't really know what I'm doing here.

Cheers

Iain

[izzywithus]

If I remember rightly when the autolube was removed from the old twinshock models, the carbs needed jetting changes (maybe just the main jet) as going to pre-mix alters the petrol/air mix, as per reason 3 above.

If I can find my TYZ manual I'll look up the jetting and you can compare to your carb

Hi Woody that's great. Could you also tell me what carb you have on your bike? I am still trying to workout the differences between the models.

Thanks

Iain

[stork955]

Gday Iain, running pre mix alters the fuel/air mix in that it is leaner. This is because in the same weight of fuel there is less fuel as oil is now present. I removed the oil pump from both my twinshocks (250 and 175) and had to make no changes to carb settings however. Plug readings indicate perfect mixture (coffee brown spark plug). Perhaps I was just lucky. As Feetup said the most important thing first up is to make sure you have blocked the port that the oil used to enter the inlet manifold. This of course will suck in air unless it is blocked and will make starting and slow running very poor. It wont however affect high speed running very much. If you have troubles after this first step make sure all the basic things are OK before doing anything else - check the air cleaner element and re-oil it (not too much oil!) Check ignition is OK etc and correct spark plug as recommended by the manufacturer. Then see how it goes. If still poor, ride the bike as much as possible in the range that is bad and note - the throttle opening amount, then kill the engine, remove the plug and have a look at what colour it is. (This is called a Plug Chop). This will tell you what the mixture is like at that point. Changing the main jet will only change full throttle mixture so it is rarely an issue. If you do need to do anything, it will most likely be a needle adjustment with its circlip. Let us know how it goes.

Cheers,

Stork

[izzywithus]

Hi Stork, thanks for the explanation.

I am as sure as I can be that there is no air leak either from the old oil inlet or around the air box carb junction or the engine side. The bike starts as it always has, first or second kick, no problems. It runs fine up to quarter throttle then starts to run rough. It produces a lot of exhaust at all throttle openings.

As per your e-mail I checked the air filter, the ignition is on the same mark as it has been and I used a fresh batch of 2T mixed as accurately as I could (50:1 synthetic Castrol). The needle clip is set on the lowest point on the needle so I can't lift it further.

I will try a plug chop tomorrow.

Cheers

Iain

[woody]

You have the needle at its richest setting so that won't help matters at the throttle openings you are having problems with.

I'd guess that the problems you're having are just due to having to reset the carb jetting from autolube to premix - assuming the bike was running fine before.

These are the settings from the manual for a 4GG bike, carb is the same as yours, a TK, although not the autolube version.

Main jet - 165

Air jet - 2.5

Needle - 5C77

Needle clip position - 3

Needle jet - S85

Slide - 2.0

Air screw - 1 to 1.5 turns out

Starter jet - 0.7

Float height - 21 - 23mm

The mix of 50:1 Castrol TTS is fine as that is what I ran mine on with no problems although you can go to 80:1 if you wanted which is the recommendation from Yamaha for TTS.

Edited February 11, 2010 by Woody