GPZ500s running like a bagowank

[stinkwheel]

Well, it has been for a couple of weeks now.

Starts first push, tickover steady and regular, pulls away no problem.

Once the revs hit about 5k it all goes pear-shaped, stuttering, misfiring, no power. Dropping a cylinder periodically. Now if you persist and twist the throttle wide open it clears its throat and winds itself up like a good-un, top end (from about 7.5k) is as normal.

Now I was assuming this was down to a torn carb diaphragm so I ignored it 'till I had time to have a fiddle.

Checked them out today, tip top condition, sliders freely moving, needle where it should be and undamaged. Bugger, what now?

Well since I'm in there I'll have a look at the air filter. Not checked it for quite some time (I tend to assume that the bike will tell me when it needs a clean). Oh bugger!

https://www.bikechatforums.com/files/airfilter_306.jpg

Well, cause or effect?

I've pulled the carbs to give them a clean up, what else will it have gone with?
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kickstart]

Hi

Errr, backfired through the carbs? But that would leave it a bit toasty and I presume it isn't as you haven't mentioned it.

My guess would be it is just suffering from old age and being cleaned with god knows what solvents in the past.

Don't think they are that expensive from Kawasaki. Bought one for Charlottes GPZ years ago (and never used it).

All the best

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

[stinkwheel]

Well, frankly it is totally minced. It could have backfired through the carbs, difficult to tell.

I'm hoping this is what is causing it to run like shite though, not a result of it.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kickstart]

Hi

Quite probably, but also possible some of the remains have blocked some passages in the carbs. Possibly even hanging around one of the throttle plates.

All the best

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

[stinkwheel]

Right, carbs.

When you look at the airbox end you see the throttle slider in the big hole in the middle and an oval opening leading into the diaphragm chamber at the top. At the bottom, there are two small openings recessed into the body of the carb facing the airbox.

I presume at least one of these is something to do with the choke. What does the other one do? Would this cause gremlins in the midrange if it was blocked (which is entirely possible given the amount of disintegrated foam that is floating about in the airbox.)

Hows about cleaning them out? I don't have access to an airline, I usually use a butane lighter refill aerosol to blast through blocked jets. Be nice to know where I am watching for the gas coming out to show me they are clear.

This is my first foray right into the guts of CV carbs as such but I want to be damned sure they are right before I put them back as you have to drain down the coolant to take the carbs off on this bike (Hot water anti-icing system).

Main and idle jets seem clean enough, as do the needle valves, throttle vlave, throttle needle and butterfly valve. I'll check the float heights as soon as I nick some clear tubing from work.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kickstart]

Hi

Suspect that is for air to go through the pilot jet circuit.

Without an air line I am unsure what is best. If you get any easily damaged diaphragms out of the way you can try blasting them through with an unloaded air pistol (just get a blast of air). You can probably screw the jets on these.

All the best

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

[stinkwheel]

Did my butane lighter refill trick (choose correct spout diameter, press down against selected jet).

When you blow gas down (up) through the main jet, you get a plume of boiling vapour out of that little tube so it must intersect the main jet emulsion tube somewhere.

Anyhow it is now definately clear. That butane trick always impresses me a high pressure organic solvent that immediately boils at room temperature, thus increasing in volume by 24 times (and therefore reaching a huge pressure in an enclosed space), really blows out the cobwebs and costs 75p from the corner shop. Much smaller than a compressor.

I suppose the absence of anything resembling an air filter wont have been helping the carburettion either. Try the new one in when it arrives on Wednesday.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kickstart]

Hi

Hopefully that has fixed it. I would suspect that any going into the engine will not have done it the power of good (even just from the grit that was trapped in it) but would probably get burnt off / blown out fairly rapidly.

All the best

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

[riichy]

wack abit of redex in the petrol might make it abit smoother
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.......... PLOD ............ zx636 2004

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