Yamaha R1 Carbs Fitted

[HAWKNORTH]

I've fitted a set of R1 carbs on the Pinto engine replacing the 2 twin Webers. These were off another 2ltr Pinto and came with the manifold and connecting hoses. I've got a fuel pressure regulator and a choke cable on order but couldn't wait to see if the engine would fire up. With a squirt of fuel through the carbs the engine fired up after a few spins. This is a good result as I didn't do much to the carbs before fitting them. The only problem so far is that the carbs on cylinders 3 and 4 are spitting back every few second. Could this just be that the carbs need balancing. I'm reluctant to do too much fiddling about until I get the fuel pressure regulator fitted. Comments welcome as usual.

[Peter Bell]

Bike carbs do spit back a bit you may need to screw out the idle screws a bit but fit the regulator first and run it at the lowest setting because the the fuel pressure may overpower the float needle valves and cause flooding.

[knights_templar]

3 and 4 are running weak

 

agree with above, fit reg, balance throttles, set pilot screws equal, and take it to a good RR that know bike carbs, just because they came from the same set-up does not prove they were jetted correctly.

[HAWKNORTH]

Fuel regulator fitted today, set at 1.5psi. All appeared to be okay as engine warmed up. Still a few spit backs through the carbs on 3 & 4. Went for a test drive then noticed a problem. The engine revs were very slow to drop back down when taking foot of the gas. Tick over also increased to 1200rpm from 1000rpm. I know the carbs need to be set up etc, but any thoughts on the high rev problem please.

[Guest Tim Norman]

Sticky linkages?

[ozz]

I have a spring on the throttle to help it return.

 

This is because bikes have two throttle cables one to pull open and one to push closed.

[Bob Tucker]

Slow idle return is often a weak mixture and/or an air leak....

[HAWKNORTH]

I'll check the potential problems suggested. Thanks guys.

[HAWKNORTH]

Main problem appears to be getting the hoses to seal onto the carbs themselves. The lip that is available to seat the hoses is only 10mm wide and the jubilee clips are simply slipping off. The carbs are supported by a bracket so the weight is not on the hoses. I need to find more suitable clips and eliminate any possible air leaks before any other fiddling is undertaken. There's always something!

[HAWKNORTH]

Got the hoses sealed properly and what a difference. No spitting back through carbs when engine warn, and no delay in rev drop off. Now need to road test and get the carbs set up on rolling road. Smiles.