Running on 3 cylinders | 96 FZR 1000

[noodlemonkey]

Howdy All,

I'm new to this forum, so will introduce myself - I'm Gregg from Cape Town South Africa - I'm the proud owner of a nice and clean 1996 Yamaha FZR1000 with a few aftermarket parts which include, an full akrapovic exhaust system, Keihin Flat CR carbs AKA FCR's - Some headwork has been done, ports have been cleaned and casting lines removed and last but no least a performance cam of some kind - cannot find any markings on it to get a spec, although it kicks in at about 7K RPM and the previous owner mentioned he had put one in.

Right - onwards and upwards - recently the bike has started running on 3 cylinders, cylinder no.4 is dead as can be - here are the things which I've tried and items which I can rule out as possible causes:
- coils are fine, including their leads and caps - swapped cylinder no.1 and 4 - no.1 fires with the no.4 lead and cap,
- cylinder no.4's carb has been checked and cleaned, although rather clean inside
- cylinder head has been pressure tested - intake valves were leaking - had them cut and re-lapped - retested - perfect now,
- intake rubbers have been replace to ensure no air leaks
- plugs replaced just to be certain
- cam timing has been checkout about 4times... its spot on

Can anyone suggest anything else to check?
I suspect a compression leak but how can only 1 cylinder loose its compression? - I have used a "make-shift" compression tester with a wine cork and it pops just as hard as cylinder no.1-2-3

I am completely out of options and have no clue what else it could be - I know my way around bike engines, built a number of them - although this one has me at a lose,

Any help would be greatly appreciated.
Thanks in Advance

[Stig]

Is no 4 getting fuel? Wet plug etc
Are the carbs balanced?

[noodlemonkey]

Hi Stig - Yeah - Plug is wet after i test run it - also have swapped any of the other running cylinders plugs to no.4 to confirm its no a dud plug.

[Stig]

Is prob just at tickover or all way through Rev range

Also as the coils fire a pair of cylinders, have you swapped the coils over or even the leads for the same coil. I know you state coils are good but it's just something to double check n confirm it stops with no. 4 cylinder

[TomcatMJ]

Carbs cleaned? Did you check also if Valvenedles and Valveseats are ok ant not worn out? (At Mikuni Carbs thats often giving too much fuel into the carbs when they are worn out)

[noodlemonkey]

Is prob just at tickover or all way through Rev range

Also as the coils fire a pair of cylinders, have you swapped the coils over or even the leads for the same coil. I know you state coils are good but it's just something to double check n confirm it stops with no. 4 cylinder

Hi Stig - From what I can tell its throughout the rev range - when taking it for a test ride - hoping it was only at the lower end of the rev range - its dead throughout.
I've swapped the coils across to check this morning and its still dead.

Carbs cleaned? Did you check also if Valvenedles and Valveseats are ok ant not worn out? (At Mikuni Carbs thats often giving too much fuel into the carbs when they are worn out)

Hi TomcatMJ - How would i check this? possible to swap these from one of the other running cylinders? (Keihin FCR parts are very expensive in South Africa)

[TomcatMJ]

If you don't have anybody with another FZR 1000 EXUP around your area then a interchange of carbs for testing is no available solution and you will have to open the carbs and have a look on the valveneedel and the valveseats in order to see if its worn-out or not...and when its opened its already a good time for a optical check of the main jets, needlejets and jetneedles and emulsion tubes,too...
If you can se there is something clogged in the carbs, its obviously time to clean them, at least with a nylon / fishing line picking inside the jets and removing the junk inside, perhaps additional a 1-2 hour bath in industrial cleaner mixed with hot water and drying with compressed air followed by spraying some fast vanishing, water-removing brake-cleaner inside the jets channels (for removing the last drips of water out of the carbs) if no ultrasonic bath is available for the cleaning....

Edit:Keihin FCR and their Parts are in most countries more expensive than the original Mikuni Carbs and Parts, but perhaps http://www.concom1.de might be cheaper than in keihins in southafrica including the shipment, might be worth an email-question for offers

[noodlemonkey]

If you don't have anybody with another FZR 1000 EXUP around your area then a interchange of carbs for testing is no available solution and you will have to open the carbs and have a look on the valveneedel and the valveseats in order to see if its worn-out or not...and when its opened its already a good time for a optical check of the main jets, needlejets and jetneedles and emulsion tubes,too...
If you can se there is something clogged in the carbs, its obviously time to clean them, at least with a nylon / fishing line picking inside the jets and removing the junk inside, perhaps additional a 1-2 hour bath in industrial cleaner mixed with hot water and drying with compressed air followed by spraying some fast vanishing, water-removing brake-cleaner inside the jets channels (for removing the last drips of water out of the carbs) if no ultrasonic bath is available for the cleaning....

Edit:Keihin FCR and their Parts are in most countries more expensive than the original Mikuni Carbs and Parts, but perhaps http://www.concom1.de might be cheaper than in keihins in southafrica including the shipment, might be worth an email-question for offers

Thanks TomcatMJ - I took the carbs off to give everything a good clean - although there wasn't much dirt in them - I did give them a good cleaning - fishing line and all. Sadly no luck.

What are some of the ways to see if its dumping to much fuel or not at all - My thoughts would be to pull the plug and place a rag over the plug hole - start and run the bike and see if any fuel comes from the plug hole - although, I wouldn't really know what the exact amount of fuel is required.

While i had the carbs out - I reset the low range jet to the standard 2 turns out for sea level.

I'm thinking I need to get my hands on an actual compression tester to see the exact compression - that's one of the larger concerns at this point.

[TomcatMJ]

Hm..i've got an idea how to test the valveseats (if you didn't se anything neither at the fuel valve needels or the associated seats) if they are worn-out or not: Take a sheet of dryingpaper or kitchenpaper or something which might soak fluids and show you by colorchanging, take the carbs off from teh rubber-joints and wait some time until its dry at the joint-connection,then put the paper below it. Afterwards turn the ignition-key around but don't start the motor so that the fuelpump would do its job and look at the paper. The Carb where you see the biggest fuel-spot might have a worn-out valveseat or needle in its fuelchamber valve and should be checked more precise by unmounting and checking the surface for dents or scratches in the contacting area of valveseat and valve needle. At Mikuni Carbs the needle showas ways faster a wearing than the seats,but nevertheless both should be checked if fuel is dripping or running where it should have been stopped by the valve. I guess Keihin should not be so much more expensive for these parts. Aftermarket-Valveenedles for mIkunis are sometimes available for 4€ per Set (i paid this for a set made in Poland for my FZR 400 with MIkuni BDST32 and a friend for his FZR 1000 Genesis with original Mikunis around the same amount) where original Mikuni needles would take around 5€ each due to the pricelist of our local Mikuni general importer here in Germany, and Keihin should not be so much more expensive...

Edit: By the way: Did you already try to change the sparkplugs in order to be sure its not just a defective plug?

[Jordan_Ciaramitaro]

Based on your comment about the plug being wet, I would guess that carb is dumping too much fuel. Since you have already gone through the carbs, I assume you checked float height. Try this:

Disconnect fuel supply, drain the carb bowls, spray(mist, don't use too much)starting fluid just in the cylinder that is not firing. If it fires this will help narrow it down to either a fueling or compression issue.


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[noodlemonkey]

Hm..i've got an idea how to test the valveseats (if you didn't se anything neither at the fuel valve needels or the associated seats) if they are worn-out or not: Take a sheet of dryingpaper or kitchenpaper or something which might soak fluids and show you by colorchanging, take the carbs off from teh rubber-joints and wait some time until its dry at the joint-connection,then put the paper below it. Afterwards turn the ignition-key around but don't start the motor so that the fuelpump would do its job and look at the paper. The Carb where you see the biggest fuel-spot might have a worn-out valveseat or needle in its fuelchamber valve and should be checked more precise by unmounting and checking the surface for dents or scratches in the contacting area of valveseat and valve needle. At Mikuni Carbs the needle showas ways faster a wearing than the seats,but nevertheless both should be checked if fuel is dripping or running where it should have been stopped by the valve. I guess Keihin should not be so much more expensive for these parts. Aftermarket-Valveenedles for mIkunis are sometimes available for 4€ per Set (i paid this for a set made in Poland for my FZR 400 with MIkuni BDST32 and a friend for his FZR 1000 Genesis with original Mikunis around the same amount) where original Mikuni needles would take around 5€ each due to the pricelist of our local Mikuni general importer here in Germany, and Keihin should not be so much more expensive...

Edit: By the way: Did you already try to change the sparkplugs in order to be sure its not just a defective plug?

Thanks TomcatMJ - I will try and identify which is worn and possibly replace those - We dont have many importers for these parts at all.
Plugs have been swapped around a few times all seem to be fully operational - I've also re-gapped them a number of times just to be sure.

Based on your comment about the plug being wet, I would guess that carb is dumping too much fuel. Since you have already gone through the carbs, I assume you checked float height. Try this:

Disconnect fuel supply, drain the carb bowls, spray(mist, don't use too much)starting fluid just in the cylinder that is not firing. If it fires this will help narrow it down to either a fueling or compression issue.


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Jordan_Ciaramitaro Sir - I like your thinking - Although the FCR's are kept together with hard bolts including the fuel lines as circled in the attached image. - Although I might just tape the needle and seat closed to not allow any fuel in and use some quick start to see what it does.

I do have some alternative suspicions - I'm going to re-sync them as I can remember not being to careful when I removed the carb slides and from memory - the no.4 is quite a bit more closed in comparison. Worth checking out.

[Jordan_Ciaramitaro]

Ha, that is actually a better idea, did not think to simply hold the float needle closed. That will allow you to actually run the engine while trying to get the dead cylinder to fire. Faster, more accurate, and less mess I like it!

[Jordan_Ciaramitaro]

I'm curious as to what you found?


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[noodlemonkey]

Okay - so great news - Bike runs, and is running on all 4 cylinders, this is what I did,

I replaced carb no.4's needle and seat, as well as cleaned all the carbs once again, using some quick start to clear out passages and jets,

BUT - now that its running and revs up well when standing - it bogs, splatters and has no power when you put it under load...

I've made no other changes to the carbs except re-factory setting the bottom end idle jets, which are set back to what they were when I first took the carbs off - which is 2.5 turns out.

When riding the bike - it almost sounds like its miss-firing and bogs when twisting the throttle.

Any suggestions?

[Jordan_Ciaramitaro]

Make sure you didn't kink a fuel line, I do this all the time on my old Ducati.


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