Suzuki gsx750 inazuma rough/erratic idle. Please help! I've done almost everything

[wsn03]

3 hours ago, Lachie04 said:

 

Ensure carbs are clean as and play close attention to syncing carbs first  syncing at 1500 -1800 rpm

Make sure all rubbers are intact including carb to airbox rubbers I once found one which was not sealing after regluing back in was fine I'd been trying to track down the cause for ages.

 

Yes the high rpm is crucial when carb balancing, and rough idle will happen with badly syncd carbs.

Sync 1 & 2 together..... then sync 3 & 4 together..... then sinc both pairs by using the middle adjuster (sorry if you know this already, trying to eliminate all your issues) 

When you adjust the screws don't lean on them, make sure you lift off before you confirm they are sync'd. Tiny amount of lean upsets it.

[Denys]

On 4/8/2021 at 11:32 PM, Buzuki said:

- That`s OK , but even with 1,5-2 full turns backward  your engine have to run at idle very smooth , 

- must admit that I was just once successfully repair those KeiHin CVK32 carbs on one B6  , reason of malfunction was bad float needle valves , those carbs leaking the fuel like crazy , any way just checked original B6 service manual (95-99 model) picture of CVK32 slow system schematic and on that picture tip of the pilot screw is showed flat with round inner surface of the carb throat , so I think maybe before you somebody inserted wrong type of pilots screws ? ,( from my experience by many Mikuni`s carbs from oil-cooled engines pilot screws tips never peek above inner surface of the carbs throat) ,

- further I will check with ohm-meter condition of spark plugs connectors since inside of each high voltage connector is hiding one around 10Kohm resistor ,

- question , did you check condition of O-rings which is hiding between each intake boot and cylinder head ?, since after 32.000Km and 12 years of old engine they can be in very bad condition causing false air to be sucked ruining engine idle ,

- and I guess that you close those four vacuum outlets with suitable rubber caps ? 

 

Spark plugs are new and original, resistance which they showed was 8.5-9.3 kohm.

Yes, I've checked rubber caps with pressure and as well will 'starter liquid' - no leaks there.

I've checked intake boots in exactly the same way as I did with carburetors rubber caps - no leaks.

'The wrong type of pilots screws' - they look exactly the same as the new original which I've ordered

 

[TonyGee]

have you checked the pilot circuit drillings ?  the pilot jet might look clean but if theirs a bit of crap in one or more of the drilled holes then its the same as a blocked jet. 

[Denys]

2 hours ago, TonyGee said:

have you checked the pilot circuit drillings ?  the pilot jet might look clean but if theirs a bit of crap in one or more of the drilled holes then its the same as a blocked jet. 

Yes, I have. They are like new inside. 

 

[Denys]

On 4/9/2021 at 9:33 AM, Lachie04 said:

Measuring header temp is a quick hack to see carbs are set up close.

My dyno guy does it as a quick check prior to a dyno run.

They should all be relatively close

Can be used as a hack to adjust pilots also. I have a cheapo infra red to thermo to do quick checks

Colder temp = richer 

Richer carb settings run better as engine temp increases

Straight up Would seem # 4 is a bit richer or not as sync to the rest.

Pilots are not always set the same so slight differences are normal.

Ensure carbs are clean as and play close attention to syncing carbs first  syncing at 1500 -1800 rpm

Make sure all rubbers are intact including carb to airbox rubbers I once found one which was not sealing after regluing back in was fine I'd been trying to track down the cause for ages.

 

 

 

 

 

In general I've sychronized carbs for three time, one time at low revs secon time at 1500 -1800 rpm and even third time with 0.05 probe as is shown here 

The video is in russian but the idea is to synchronize carbs more precisely with 0.05 mm probe.

So in the end I'm sure that my rough idle is not because of the wrong synchronization.

Edited April 10, 2021 by Denys

[Buzuki]

Denys

Your measured spark plugs resistance is OK but I was thinking on spark plug caps (connectors) internal resistance , which have to be around 10Kohm measured from connector end to end ,  picture shows internal piece order , resistor (pointed with red arrow), spring , and brass screw , that (RFI) supresor resistor sometime loose his resistance causing weak High Voltage spark , which can be bad both for engine correct run and also bad for ignition coil correct load .

ps, did you check for correct mutual position of both camshafts vs cranckshaft ? 

Edited April 10, 2021 by Buzuki

[Denys]

4 hours ago, Buzuki said:

Denys

Your measured spark plugs resistance is OK but I was thinking on spark plug caps (connectors) internal resistance , which have to be around 10Kohm measured from connector end to end ,  picture shows internal piece order , resistor (pointed with red arrow), spring , and brass screw , that (RFI) supresor resistor sometime loose his resistance causing weak High Voltage spark , which can be bad both for engine correct run and also bad for ignition coil correct load .

ps, did you check for correct mutual position of both camshafts vs cranckshaft ? 

Sorry in previous reply I meant not spark plug but spark plug caps, I bought all 4 new and original exactly like this one https://www.bike-parts-suz.com/suzuki-motorcycle/assignment_spare_parts/3351048B10000 

Position of camshafts vs cranckshaft is exactly as it should be according to manual.

[Buzuki]

Last thing what come in my mind and can cause unstable engine run is the ignition box , so if is possible try to swap him with another original ignition box ,  but before you swap that box inspect his connector contacts for corrosion . 

[Denys]

9 hours ago, Buzuki said:

Last thing what come in my mind and can cause unstable engine run is the ignition box , so if is possible try to swap him with another original ignition box ,  but before you swap that box inspect his connector contacts for corrosion . 

Yes, I've already ordered another used ignition unit but it seems to me that box can either give ground to coils or not to give, there is no way that it can give bad or insufficient ground to the coils.

 

[Denys]

On 4/8/2021 at 2:15 PM, wsn03 said:

Whoaoh! Somethings wrong there. The revs changing. Not good. So that box leaking is causing a surge of air. Can you seal it?

Revs was changing exactly in the same way even when air box with rubbers was disconnected from carbs.

[Buzuki]

32 minutes ago, Denys said:

Yes, I've already ordered another used ignition unit but it seems to me that box can either give ground to coils or not to give, there is no way that it can give bad or insufficient ground to the coils.

 

Just one more thing ,on the fully warm and idling engine did you try to wiggle TPS (Throttle Position Sensor) left and right and see the influence on engine idle stability ? 

[Denys]

36 minutes ago, Buzuki said:

Just one more thing ,on the fully warm and idling engine did you try to wiggle TPS (Throttle Position Sensor) left and right and see the influence on engine idle stability ? 

Yes, I tried that, but the picture of erratic idling wasn't changing anyhow during TPS adjusting, the resistance of TPS is exactly as it should be according to the manual for open and closed throttle.

[Denys]

Just now, Denys said:

Yes, I tried that, but the picture of erratic idling wasn't changing anyhow during TPS adjusting, the resistance of TPS is exactly as it should be according to the manual for open and closed throttle.

I'm still thinking that the problem is with pilot jets (probably I haven't cleaned them enough) and pilot screws, a new set of which will be in my hands in 2-3 days, ignition unit in 5 days, actually those are the last items which haven't been replaced yet

[Denys]

So, the problem was in pilot jets and screws which I've replaced with a new set, idle is smooth right now without any erratic jumps... Adding macro photos with new jets on the left and old ones on the right. Thank you everyone for help!!!

[ayush]

Im having  a problem with my gsx 750 inazuma. Im having a loss of pickup as i accelerate. What could be the possible reason for this? Can anyone help?