R1 Carb 1.4 Bottom Vtr Head

[Low_slow 0]

Hello iv setup some r1 carbs with a 1.1l gearbox 1.4 xs bottom end and a vtr head.

Iv got a huge flat spot at 3k and can get rid of it iv moverd the cerclip on the needle and made a small difreance but not enough I'm trying to get it all sorted before ptm show at Santapod! Any ideas for a solution?

Has any 1 had a similar problem with a 1.4 tu?

 

Thanks

[allye 530 3 Cars]

What fuelling method are you using?

[Low_slow 0]

I was using the mercanical pump that was on my 1.4 head but I'm now using an electronic 2-3psi fuel pump and upto 1.5l a min.

 

I was using the mercanical pump that was on my 1.4 head but I'm now using an electronic 2-3psi fuel pump and upto 1.5l a min.

[trogboy 17]

VTR as in Saxo VTR? That's a 1600cc motor isn't it (TU5JP from memory) Can you bolt that head onto a stock TU3(s) bottom end without the compression being very low due to the bigger combustion chamber? Like 8 point something to 1 from memory.

 

Don't think that that would neccessarily give you a flat spot but wouldn't it make decent power difficult?

[allye 530 3 Cars]

Do you not need to use domed pistons from a 106 xsi to use a vtr head on a tu3s bottom end.

[unariciflocos 49 1 Cars]

Mid range is adjusted by the circlips. Is it lean or rich?

 

To richen the mixture you need to move the circlip lower towards the tip of the needle. To lean it move it up. If this fails you need custom needles.

[Low_slow 0]

VTR as in Saxo VTR? That's a 1600cc motor isn't it (TU5JP from memory) Can you bolt that head onto a stock TU3(s) bottom end without the compression being very low due to the bigger combustion chamber? Like 8 point something to 1 from memory.

 

Don't think that that would neccessarily give you a flat spot but wouldn't it make decent power difficult?

Yep saxo tu5 and tu3 bottom!I'm hoping to do a compression test tonight I shall let u know! And yes fits straight on no problems! Befor I rejected the carbs I seem to keep up with a friend who has a standard 1.4

[Low_slow 0]

Mid range is adjusted by the circlips. Is it lean or rich?

 

To richen the mixture you need to move the circlip lower towards the tip of the needle. To lean it move it up. If this fails you need custom needles.

I have moved it I think I might have to they some aftermarket ones! Coz iv tried them all and I right up to top at the moment and any lower and it hardly runs!

[unariciflocos 49 1 Cars]

I'm sorry but I don't understand what you wrote there.

 

R1 carbs may be overkill for a 1.4, they're rated for 160 bhp standard on the bike so I'm guessing yours is rich. My mi16 on R1 carbs had an AFR of around 9 mid range at one point with 14.7 being the optimal and around 12.9 at wot.

[Low_slow 0]

I have moved it I think I might have to they some aftermarket ones! Coz iv tried them all and I right up to top at the moment and any lower and it hardly runs!

Sorry what I meant to say was: iv moved the circlip to every position and it runs best at the top! A friend did the same conversion on his 1.3 309 on a ohv engine and made some reasonable power!

Iv ordered some smaller jets to drill again but move the cerclip down while drilling!

[unariciflocos 49 1 Cars]

I'm not sure that's the best approach. When setting up these kinds of carbs you start with the main jets and see how the car performs at wide open throttle and high revs. That's how you see which mains you need.

 

After that you move onto the needles. At WOT needles are fully retracted. At mid range needles are partially inserted and control the amount of fuel the carb delivers. If your car runs best with the circlip at the top then it'll be running rich just as I said. Running the aftermarket jets won't help, assuming they'll have been made for a high performance bike that probably delivered 160 170 bhp. Your engine will never deliver that power and therefore will never need that much fuel. Best find the original needles which I assume will be a bit longer and maybe just a bit thicker.

 

Lastly you set up idle and low revs, where neither the main jets or the needles do anything. There it;s a question of air corrector jets that you need to adjust.

 

Good luck! I know i abandoned trying to setup my carbs after 8 hours on a dyno with an AFR gauge.

[burr_2000 1]

every time i read a build like this it brings back memorys. If you use search, theres plenty of tips and advice on how to tune or modify a TU for best use. People think by plonking a bigger valve head and fitting big carbs will make it quicker. The challenge boys get impressive figures by using standard engines. To componsate for the dished pistons you would need a heavy skim of approx 1.2mm to raise the CR to 10.3:1