Post Valve Check/Shim, Running Lean

[dandywarhol]

Try the original ECU?

[Overlord Neil]

That occurred to me as I was writing, but wife's patience only stretches so far, so I'll have a crack at that tomorrow. I was hoping Cobba would be able to give a definitive yes/no.

[Tarwetijger]

Are you sure all vacuum lines are set up the right way?
It just seems odd to me.

[Overlord Neil]

Had another crack at the bike this afternoon;

Put the original ECU back on.

Checked the Vacuum hoses off the inlets but I'm using an auxiliary tank so these aren't doing anything and blocked off.

Took the inlet stubs off the cylinder head and applied some liquid gasket to ensure a seal, reattached.

Put a bit of liquid gasket around both sides of the carb mounting boots.

Still the same. I noticed that it is blowing back through the carbs occasionally, sometimes pretty violently to the point where it blew the #1 carb off the boot. I've triple/quadruple+ checked the valve timing and its good.

When I'm trying to slow open the throttles the plate attached to the diaphragm is almost a blur, its definitely not a smooth movement.

I'm wondering if there is something fundamental with the carbs, something I've missed during rebuild. I'm not going to buy another set of carbs until I can narrow down the carbs as the problem.

[dandywarhol]

Check pipe #68 vents to atmosphere and the O ring #8 is in place

https://www.cmsnl.com/yamaha-trx850-199 ... ml#results

[Overlord Neil]

Checked both pipes, all clear. Blowing through [back towards the carb] the diaphragm lifts the needle fully, same happens on both carbs so the pipes and the circuit are clear and venting to atmosphere. I checked the O-Rings (#8), present and correct. Any other thoughts?

[dandywarhol]

Fuel injection

[cobbadiggabuddyblooo]

Check your voltage on the battery , then again under load when starting and continue to check it as you wind open the throttle and the motor dies...
At least you can see if there has been any damage to the alt, rectifier or battery by putting the batteries in series.
IGNITECH can cope between 10-19v...

The std ECU gives the same problem so see if you can follow the food chain and eliminate the electricals.
Look at your coil earth too. It may be be loose and easily bumped digging around while doing the top end.TRX runs a Wasted spark and it's igniting the unburnt fuel so I'm taking a punt on the intermittent coil earth or connector.

[Overlord Neil]

Shock horror, it starts... and rides.

It occurred to me that (because I'd only done a partial rebuild) the engine wasn't getting warmed up because I didn't want to run the thing with no cooling for too long. Unable to think of anything else I could do, though I did put the original needles back in on the Factory Pro emulsion tubes and standard jetting, I completed the assembly and filled it with coolant. The battery is too shot to fire her up so I connected it up to the car and she fired up straight away, let it warm up for a while then tried to pick up the revs, if I cracked her WOT it would bog and stall but slowly creeping the revs got it to about 5-5.5k a few times. Then 'something' happened and she roared, red lined strong and hard.

Figured I'd chance it and take her for a spin around the block, she still bogs horribly between 2.5-4 then takes off like a scolded cat, but its definite progress.

The only other problem I faced was the fan not kicking, does the fan start signal come from the temperature sensor on the water pump, the gauge or is there another sensor? I did check all the fuses (just in case) and the connections all look like they are complete.

Any suggestion on either problem? Thanks to all that have helped me get this far.

[dandywarhol]

Check the TPS is set correctly for the hesitation

Is the cooling system pressurising? If it isn't then the fan will probably not come on. The fan comes on near to boiling point unpressurised. When the system is pressurised, the boiling point of the coolant rises and won't boil to around 120 degC

[cobbadiggabuddyblooo]

Look to see if the tiny black earth strap is attached to the body of the water pump. Thermo switch lives on top of the pump with a 2 pin connector. It should kick in at 105-107*. Double check there is no air lock as Dandy says. If no response by 110* shut it down. Unplug the fan and attach 2 wire directly from the battery to see if it turns on. If all good follow the food chain back and you can check the switch via the manual or while the bike is hot and when cold to get your values.

[Overlord Neil]

Dandy/Cobba, many thanks guys. Yep can confirm its pressurised, the carb heater return pipe came off and gave everything a high pressure hose down. I was stopping too soon, I let the gauge climb to 100 deg so might have just shut it off too early. I'm using Comma Xstream G30 ready mix.

I was careful not to move the TPS, though I might have a play with the Ignitech settings and check its reading in the right places. If I do need to move the TPS, is there a method of moving it 'correctly'?

[cobbadiggabuddyblooo]

Don't move the TPS because you set the 0% to 100% values on the IGNITECH not like previous with the std ECU where you have set values and manipulate the TPS to get within the thresholds of 0-100% throttle.