Balanced throttle bodies, still running rough

Message

szrdave · #1 Post by **szrdave** » Tue Aug 30, 2011 6:38 pm

I took the bike to a Honda dealership where I used to work, and a friend of mine from the workshop gave me a hand to balance the carbs.

Looking at the manual (now I'm home) it seems the earlier Falcos didn't have vacuum take-offs on the throttle bodies. We disconnected the intake pressure sensor and used the ports to connect the balancer, the readings were quite a way out but balanced up nicely.

I took the bike out for a road test and it's lumpier than before! It hiccups when getting back on the gas from a closed throttle, and occasionally dies when picking up from idle.

Obviously the sensible option is to pay Aprilia a small fortune to have a look at it, but having always worked on my own bikes it goes against the grain.

Not to mention the cash could be spent on an end of year track day!

Any thoughts?

Aladinsaneuk · #2 Post by **Aladinsaneuk** » Tue Aug 30, 2011 6:40 pm

Book it into griff

( oh, look at doing the same thing on an early Mille engine - I think you will find the right procedure then)

anzacinexile · #3 Post by **anzacinexile** » Wed Aug 31, 2011 7:31 am

You did remember to plug the sensors back in I suppose

D-Rider · #4 Post by **D-Rider** » Wed Aug 31, 2011 7:52 am

It's not just a case of balancing the TBs but making sure that the air bypass screws are set within a reasonable range - otherwise you will mess up the air/fuel mixture at small throttle openings.

This is best done using a CO meter as well as the vacuum gauges ..... but few of us have one of them - so it's a case of trial and error.
I think that somewhere (workshop manual ?) it may be noted the nominal start point for this - ie how many turns the bypass screws should be opened.

szrdave · #5 Post by **szrdave** » Wed Aug 31, 2011 11:31 am

It has occurred to me we balanced the TBs but didn't reset the TPS. I'll do it tonight and see if it helps.

D-Rider - When you say air bypass screws, do you mean the screws used for balancing? I didn't actually check how many turns out they were, but it won't be more than 2.5.

D-Rider · #6 Post by **D-Rider** » Wed Aug 31, 2011 7:54 pm

szrdave wrote:It has occurred to me we balanced the TBs but didn't reset the TPS. I'll do it tonight and see if it helps.

D-Rider - When you say air bypass screws, do you mean the screws used for balancing? I didn't actually check how many turns out they were, but it won't be more than 2.5.

Yes - they are the ones.

TPS is unlikely to have moved TBH but worth checking.
Read the workshop manual on how to do this - it's important that you set things up right before you look at the diagnostics.