Throttle body balancing

conkerman · Post by **conkerman** » Fri Jun 21, 2013 9:05 am

Based on experience with a different bike have a look at the following.

-Cam timing.

-If you know anyone with a gas tester have a look at the CO at idle.

My triumph Daytona was running like a bag of crap, I discovered that the injectors were all over the place. Bike was running lean with lean pops, misfiring and very, very hot exhaust.

Awaiting more of an expert view.

gus · Post by **gus** » Fri Jun 21, 2013 9:54 am

Hi
Have you checked the rubber covers on the throttle bodies where you coneect your gauges for balancing are not split or perished.?
I take it you set your valves to 0.15 inlet and 0.30 mm exhaust.
All the best
Gus

Bikerhoss · Post by **Bikerhoss** » Fri Jun 21, 2013 10:17 am

gus wrote:Hi
Have you checked the rubber covers on the throttle bodies where you coneect your gauges for balancing are not split or perished.?
I take it you set your valves to 0.15 inlet and 0.30 mm exhaust.
All the best
Gus

Yup, valves as you say. The vaccum take-off covers seem to be ok ta.

nab 301 · Post by **nab 301** » Fri Jun 21, 2013 8:11 pm

If it was an airhead, advice on the net would suggest tight/leaky exhaust valves.. What did you set the endfloat at ?
Other suggestions were, lambda sensor or TPS. What about the air temp sensor?

Maybe disconnect the lambda sensor?

tanneman · Post by **tanneman** » Mon Jul 01, 2013 2:01 pm

Seeing that your bike is older than mine being single spark maybe you should pull off the rubber covers and have a good look if it is perished. My bike started to feel a bit rough and won't hold revs at a steady throttle and sometimes struggled to start when hot. The LH cylinder spark plug was white indicating lean running while the RH one was dark brownish colour. Did the throttle body sync today with a mechanic friend of mine just for me to pick up a bit of experience doing it. I do most of the maintenance myself. When we fitted the vacuum gauge the idle immediately smoothed out and I had a good look at the covers, Yep they were gone. A small adjustment on the LH brass screw brought it in. Fitted new ones and it is as smooth as a twin can be.

Just out of interest we hooked up the exhaust probe and the measurements were very low. CO = 0, CO2 = 14.7 (between 12 to 16), Hydrocarbons = 60 or 0.60 must not be more than 120.

Other usual suspects can be dirt on the cam pulleys, sticky fuel cable, dirty throttle body valves and brass screws, idle cable adjustment or TPS sync if the fault is related to the throttle bodies and fueling. More serious stuff can be a burnt valve (or held open) or bent pushrod. Last one you would notice when trying to set valve clearance.

Much more I can't help. Gus or steptoe is the guys to speak to.

Bikerhoss · Post by **Bikerhoss** » Fri Jul 12, 2013 10:56 pm

Thanks again guys,
O2 sensor unplugged, cleaned, tried again, Same coughing with or without it. 2nd hand HTs and coil tried, no difference.
Valves def seem to be right clearance, End float at 0.1mm.

To test the injectors, can I just unplug them, clean them, and see if they spew fuel, or is that too DIY?

Same for brass screws, can I just take them right out to clean up?

PS I did pm the guru, but not heard back as yet

Dai wiskers · Post by **Dai wiskers** » Fri Jul 12, 2013 11:09 pm

The big brass screws just unscrew I'm trying hard to remember if they have o'rings fitted (I'm pretty sure that they do )
O'rings are fitted between the throttle bodies and inlet manifold's but i think you have checked for air leaks

nab 301 · Post by **nab 301** » Sat Jul 13, 2013 8:56 pm

Only re reading this now , have you actually changed the fuel filter? Also Had a good look on UKgser and similar problems were caused by TPS sensor or in one case a break in the loom (wires leading to the TPS) . There was one thread however with similar symptoms(not revving under load) which ended up being the fuel pressure regulator. The onset was more sudden than your symptoms though . The fuel regulator sticks open apparently so clamping the return pipe temporarily will alleviate the symptoms for diagnostic purposes only

cornishflat · Post by **cornishflat** » Sat Jul 27, 2013 7:20 pm

nab 301 wrote:All of the above is correct to a certain extent. You've got to the stage where you need to hook up the gauges of your choice , twiddle a few screws and adjust cable adjusters and actually see and hear what differences they make.
At idle you need the throttle cables and fast idle cable to be just slack enough to allow the throttle bodies to be fully closed.
Idle speed is controlled by the the air bypass ( brass) screws. If the bike is running reasonably ok you will probably only need less than 1/16 of a turn on one side to balance and keep the idle speed in spec. If however (depends on the bike ) when you balance it at idle, the idle speed is incorrect, you'll have to adjust both brass screws equally to increase /decrease the idle speed . (it's also unlikely both screws will remain in identical positions) (Sometimes it helps to remove the screws and clean out the orifices with carb cleaner if there's a problem balancing) That's the easy bit...

When you open the throttle , the primary cable is linked to a junction box which splits into two cables, one for each TB. This is where all the innacuracy can develop. Basically you're attempting to synchronise these cables while also compensating for any mechanical imbalance between the cylinders at 3 to 4 k rpm (using the vacuum gauges to show what's going on). If and when you get to check yours , you'll figure out quickly enough that minute adjustments only are needed which is why adjusting one side only can simplify things. (Without stating the obvious for example , if the left tb is opening early as indicated by the gauges , you can tighten the right hand cable or loosen the left hand , it doesn't matter , once the cables aren't holding the tb's open at idle)
This is where you need all the outer cables to be seating correctly and the cable adjusters to be lubed and corrosion free , and in extreme cases to clean the cable quadrants, because any dust /grit imbedded here can affect the balancing .
Again, one cable is all you really need to adjust, but as you found out by researching, tightening the cable locknut can affect the readings dramatically.
With time, you'll learn how to compensate when tightening the lock nut.(it's just something you'll get a feel for)
On a low mileage garaged bike this is all generally easy enough , it's when you get to 100k miles with worn tb's , valve guides etc that the fun starts #
Alternatively if the bike appears to be ok , just ride it and ignore all of the above ramblings....

Nice write up ned. Done mine today using a Carbtune and its easy enough with practise. As you say when tightening the locking nuts on the throttle body cables the cable adjuster tends to want to move as well...long nose pliers were my cure. On test the bike does feel a little smoother particularly going from off to on the throttle.

Nice one

boxerscott · Post by **boxerscott** » Sat Jul 27, 2013 8:53 pm

feralworks wrote:I have the full blown BMW 'SYNCHRO' diagnostic machine & a damned clever box of trix it is too
Ignoring all the fancy diagnostic graphs it can produce, it incorperates an electronic balancer (which displays as a bar graph) and is therefore similar in technology to the Harmoniser.
I now use this on EVERY bike as the balancing that can be achieved with these modern electronic balancers is nothing short of incredible & makes the old dial vacuum gauges positively agricultural. The more cylinders you have to balance, the more impressive / easier it gets!

In the end it's all down to cost though - can you justify the expense for the amount you're going to use it ??? Having said that, the cost difference between a set of gauges & an electronic balancer is narrowing all the time.

- Come to think of it, anybody want to buy a set of 'retro' synchronising gauges??

Aye, sell those then you have nowt to cross check your carlos fandango ones once they go out