Bike Carb Queries For Tu3 Engine

[Guest spanner87]

hi guys, after having nothing but trouble from solex carbs,im planning on running bike carbs on my xs and have a few queries for tuners of the forum, here goes.

 

first up does anyone know the inlet valve sizes on the tu3s head and the standard tu3 head?

the ideal tuned lenght from the inlet valve to the carb mouth as im fabricating my own custom inlet manifold?

ideal carb inlet size for the 1360 engine nd valve size relation for the carbs?

what to do with the brake servo pipe and various vaccums?

standard fuel pump pressure and if its safe to fit a regulator on it?

if the standard fuel pump is too powerful (3.0 psi maximum!)

if it is too powerful would it be suitble to remove the fuel pump and make a blanking plate?

 

has anybody done this conversion before and willing to share experiences and tips? photos would be greatly appreciated too!

[swordfish210 20]

hi guys, after having nothing but trouble from solex carbs,im planning on running bike carbs on my xs and have a few queries for tuners of the forum, here goes.

 

first up does anyone know the inlet valve sizes on the tu3s head and the standard tu3 head?

the ideal tuned lenght from the inlet valve to the carb mouth as im fabricating my own custom inlet manifold?

ideal carb inlet size for the 1360 engine nd valve size relation for the carbs?

what to do with the brake servo pipe and various vaccums?

standard fuel pump pressure and if its safe to fit a regulator on it?

if the standard fuel pump is too powerful (3.0 psi maximum!)

if it is too powerful would it be suitble to remove the fuel pump and make a blanking plate?

 

has anybody done this conversion before and willing to share experiences and tips? photos would be greatly appreciated too!

 

1. No idea

2. As long as you can get it

3. Find a set of carbs with a 40mm choke and you should be ok

4. My manifold has take offs welded on for the vac advance and the brake servo

5. Not sure what the standard pressure is

6. I cant imagine it being too powerful

7. Yes i made a plate to cover the old pump and i'm using a Facet Solid State pump.

 

I'll take some photos soon and post them up here of everything i can think of.

[M_R_205 5 1 Cars]

The standard pump should be ok as it has a cut off when it get up to pressure, stick a guage on to mesure hwat that is, and fitting a regulator shouldnt be a problem, if you still decide to go for an aftermarket pump use the R1 pump (if your using R1 carbs) as it is perfectly suited for the carbs running the correct pressure/flow and has a cut out also.

 

i cant answer most your question but what i will add is as its at the back of the engine bay you have a fair bit of room, try and make the manifold so the carbs sit at the standard (ish) angle which is about 45 degrees as iv had a nightmare re setting the float levels to stop them overflowing,

 

 

Hope this helps

Paul.

[swordfish210 20]

The standard pump should be ok as it has a cut off when it get up to pressure

 

The standard pump doesnt have a cut off as it's a mechanical pump.

[M_R_205 5 1 Cars]

The standard pump doesnt have a cut off as it's a mechanical pump.

 

You sure?? i thought it worked on a freewheel system only engaging when there was a drop in pressure, as when you hold the pump and pump it manualy with the outlet blocked the arm goes light with no resistance...

[Mark205 1]

The standard mechanical pump will contantly pump, but the solex carb would not take more fuel when the chambers are full.

It doesn't cut off it just cant pump more fuel in when the chamber is full, when ideling for example.

 

I was going to put bike carbs on my xs, but i bought a gti engine before i started and then the engine block cracked before i got a chance to fit any so i converted to 1.9 8v on carbs instead.

 

The manifold for bike carbs has to be angled loads on the tu3s because the engine mount is in a bad place.

[swordfish210 20]

Custom engine mount is the way around that. Colin Satchell makes them

[M_R_205 5 1 Cars]

The standard mechanical pump will contantly pump, but the solex carb would not take more fuel when the chambers are full.

It doesn't cut off it just cant pump more fuel in when the chamber is full, when ideling for example.

 

2 against 1, it looks like i stand corrected.

[Guest spanner87]

thanks for the replys guys if anybody has pics of their setups and benchmarks to start from with drilling the jets it would be greatly appreciated!

 

power is really down at the moment i had a saxo 1.1 (60.8 hp at flywheel) go past me relativly easy yesterday and it kinda put a downer on it lol.

 

i love the sound of bike carbs tho

 

swordfish do you by anychance have a link to the fuel pump your talking of? im used to tuning bikes and 2 strokes so some of the gear involved is new to me

 

Paul - i will have a look for an r1 fuel pump as well to compair the 2,are you running bike carbs on a tu lump as well???

[swordfish210 20]

This is the one i'm using:

 

http://www.merlinmotorsport.co.uk/p10864/S...oduct_info.html

 

You can get them cheaper than that if you shop around for it.

[swordfish210 20]

Some pics for you, ignore the dirt :

 

The carbs:

 

Takeoff for the servo:

 

Takeoff for the vac advance:

 

Throttle cable bracket:

 

Air filter backing plate attachment:

 

And the custom engine mount:

[Guest spanner87]

thanks swordfish,just what i needed!!!!

is that a 1360 lump also?thats a nice piece of kit,is there a specific reason people make the manifolds out of ali/stainless? as i was thinking of making one from steel and getting the inside chromed and the outside powder coated.

which carbs are they?R6???

 

thanks for your time and patience mate.

[swordfish210 20]

Yeah it's a 1360 engine, it looks ok but it's a complete dog of an engine really, i'm building another which should be a much better one. I think they're aluminum to minimise fuel dropout, yes they are R6 carbs but my advice would be to avoid them. Try to get a set of Mikomi carbs from a Suzuki as they are much better quality and they are easire to set up/tune.

[Anthony 1,003]

first up does anyone know the inlet valve sizes on the tu3s head and the standard tu3 head?

TU1, TU3, and TU3S heads all share the same valve sizes - 36.8mm inlet and 29.4mm exhaust.

 

The only TU3 that I know of with bigger valves is the 106 XSi (TU3J2?) which has the same sized valves as the TU5 engines.

[AdamP 0]

Try to get a set of Mikomi carbs from a Suzuki as they are much better quality and they are easire to set up/tune.

 

Mikuni

 

Plus they appear to be better spaced for the head as the suzuki engines are a bit wider.

 

 

those are Mikuni 40s off a late carbed GSXR1100,

[swordfish210 20]

Mikuni

 

Bloody pedantic

[Guest spanner87]

thanks for the help guys, some nice pics there was there an improvement using these carbs over the solex?economy or power?

[swordfish210 20]

Power: Oh yes. Noise: Oh yes. Economy: Best to be ignored