ZXR750H1 - Low Speed Rough Running - Airbox

[BanditsHigh]

Following on from previous post ( https://www.bikechatforums.com/viewtopic.php?t=168381 ) ...

Right carbs out and cleaned, but still rough running at low revs.

When looking at the airbox to carb rubbers three of them are deformed as is the airbox where they sit.

If you can see from the pics, the rubbers should form a seal between the main air path and the slow speed circuit at the bottom of the carbs ... they should sit in the groove around the main air path.

Would anyone care to agree with me that due to the deformation of the rubbers/airbox that the main air path will be drawing air from the slow speed circuit thereby preventing correct operation ... or you can tell me I'm talking crap and explain why

All the best ... Barry

Pic#1: Far right carb rubber and airbox the way it should be, whereas all the others are deformed.
https://i16.photobucket.com/albums/b9/BanditsHigh/Carbs001.jpg

Pics#2/#3: Airbox flipped round to show the deformation in three out of the four rubbers and also the deformation of the airbox itself.
https://i16.photobucket.com/albums/b9/BanditsHigh/Carbs002.jpg
https://i16.photobucket.com/albums/b9/BanditsHigh/Carbs003.jpg

Pic#4: The carbs showing where the airbox carb rubbers attach.
https://i16.photobucket.com/albums/b9/BanditsHigh/Carbs004.jpg

[Bikeless]

I'd pretty much agree with your diagnosis, .

[BanditsHigh]

Thanks for you opinion ... I can possibly trim the air box down to get rid of the 'stick-i-oot' bits caused by the deformation, but the rubbers are also a bit gubbed.

Sounds like another airbox/rubbers is the way to go

[Kickstart]

Hi

Not sure that the air mixing from one to the other should matter that much. However I would suspect that the deformed bits would land up blocking some of the jets.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[BanditsHigh]

^^^ More along the lines of air being drawn away from the circuit (partial vacuum?) than air mixing ... and yes, also the possibility of blocking

[Barry_M2]

From when it was running ok, to when it starting running rough, had the airbox been removed?

ie: Did you remove and refit the airbox and then it started running rough?

To be honest, I suspect blocked idle / slow speed jets.


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ZXR750R (M2) - For the road.
CBR1000 RR4 - For the track.
https://www.bikechatforums.com/profile.php?mode=viewprofile&u=4332

[BanditsHigh]

^^^ Nope, been like this since I bought/sold bike.

Once above 3k the engine pulls nice and strongly, just doesn't like having the idle set correctly, as that's when it'll hang at 4k revs if you blip the throttle.

All the best ... Barry

[Barry_M2]

More than likely the pilots then. Then control fueling up to around 3k, then the mains take over.
____________________
ZXR750R (M2) - For the road.
CBR1000 RR4 - For the track.
https://www.bikechatforums.com/profile.php?mode=viewprofile&u=4332