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Go Back   FZ1OA Message Board > FZ1 & Fazer Owners Association > Exhausts, Carburetion & Performance > Gen 1 Exhausts, Carburetion & Performance

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Old 07-01-2019, 02:40 PM   #1
six5monza
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Can I check / change diaphragms with carbs still on the bike?

It has been a while since I posted, which just shows how reliable my bike has been! I tend to ride and forget it.

However, last time out, I ran into a problem in that the bike wouldn't rev beyond 8K. It was especially noticeable when grabbing a handful of throttle. It would just bog, feeling like a misfire.

This is a 2001 with 63K miles on the clock. Ivan's kit, GYTR slip on, AIR removal kit. Dyno'ed at a hair off 130 BHP when it was much younger and fresher, but same spec as it is now.

I have a set of plugs, air and fuel filters to get basic service stuff out of the way, and a spare coil pack to allow me to do some testing for ignition issues.

The EXUP valve moves freely, resets as expected at ignition on, and there is no 7K signal on the tach. I am pretty sure the cables are connected the right way around too...

Browsing the forum and talking to the local bike shop leads me to another possible cause; one or more leaking carb diaphragms. I looked just to see if the carb tops can be removed in situ, and yes, that looks easy. There was one screw on no. 4 carb top which had worked loose, and indeed the screws holding the fast idle / choke actuation lever are AWOL, so time for some maintenance.

After all that, the question is, can I...

1) inspect, and if necessary,
2) swap out

the carb diaphragms without removing the carbs? I have seen posts saying it is a bi**h to remove them, and other posts saying it isn't as bad as those other posts make out. I am fearful of trashing the rubber boots which, like most I have seen, exhibit surface cracking. That and there just isn't a lot of room in there to work with.

One other issue... I have never synch'ed the carbs. It is possible that my local bike shop did when they did the valve clearances at 26 and c. 50K, but I don't know that for sure.

Jim M.
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Old 07-02-2019, 12:14 PM   #2
longeze
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Quote:
Originally Posted by six5monza View Post
It has been a while since I posted, which just shows how reliable my bike has been! I tend to ride and forget it.

However, last time out, I ran into a problem in that the bike wouldn't rev beyond 8K. It was especially noticeable when grabbing a handful of throttle. It would just bog, feeling like a misfire.

This is a 2001 with 63K miles on the clock. Ivan's kit, GYTR slip on, AIR removal kit. Dyno'ed at a hair off 130 BHP when it was much younger and fresher, but same spec as it is now.

I have a set of plugs, air and fuel filters to get basic service stuff out of the way, and a spare coil pack to allow me to do some testing for ignition issues.

The EXUP valve moves freely, resets as expected at ignition on, and there is no 7K signal on the tach. I am pretty sure the cables are connected the right way around too...

Browsing the forum and talking to the local bike shop leads me to another possible cause; one or more leaking carb diaphragms. I looked just to see if the carb tops can be removed in situ, and yes, that looks easy. There was one screw on no. 4 carb top which had worked loose, and indeed the screws holding the fast idle / choke actuation lever are AWOL, so time for some maintenance.

After all that, the question is, can I...

1) inspect, and if necessary,
2) swap out

the carb diaphragms without removing the carbs? I have seen posts saying it is a bi**h to remove them, and other posts saying it isn't as bad as those other posts make out. I am fearful of trashing the rubber boots which, like most I have seen, exhibit surface cracking. That and there just isn't a lot of room in there to work with.

One other issue... I have never synch'ed the carbs. It is possible that my local bike shop did when they did the valve clearances at 26 and c. 50K, but I don't know that for sure.

Jim M.
Bump...
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Old 07-02-2019, 04:55 PM   #3
NHFZ1
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I am pretty certain that I pulled the diaphragms out of my carbs with them still mounted on the bike. I don't remember drama so it must have not been to bad to scar me for life.
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Old 07-02-2019, 05:08 PM   #4
fermic37
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Yes. It’s easy. Remove the tank.
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Old 07-02-2019, 07:53 PM   #5
six5monza
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Thanks for the input. I will have a go tomorrow and let you know how it goes.
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Old 07-02-2019, 08:27 PM   #6
arkie6
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Yes, you can remove the carb diaphragms and slides without removing the carbs. A right angle dog leg Philips screwdriver (see image below) helps get at the screws near the frame rails.

But before you go to that trouble, have you checked your air filter box inlet to make sure something hasn't gotten sucked in and is blocking the air flow? Something like a rag, or piece of paper, or tie down strap, or power cord? This symptom "the bike wouldn't rev beyond 8K" is a classic plugged air inlet symptom. You might also have something inside the air filter box like a mouse nest. If you don't find something stuck in the air inlet, I would remove and inspect the air filter before I looked at the carb diaphragms.



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Old 07-02-2019, 09:37 PM   #7
six5monza
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Quote:
Originally Posted by arkie6 View Post
Yes, you can remove the carb diaphragms and slides without removing the carbs. A right angle dog leg Philips screwdriver (see image below) helps get at the screws near the frame rails.

But before you go to that trouble, have you checked your air filter box inlet to make sure something hasn't gotten sucked in and is blocking the air flow? Something like a rag, or piece of paper, or tie down strap, or power cord? This symptom "the bike wouldn't rev beyond 8K" is a classic plugged air inlet symptom. You might also have something inside the air filter box like a mouse nest. If you don't find something stuck in the air inlet, I would remove and inspect the air filter before I looked at the carb diaphragms.



Yeah, Airbox was clear. Air filter was a bit grubby but not enough to impact flow. Same for the fuel filter. Temperature check on downpipes showed no significant differences. New filters, new plugs, and EXUP check should take care of the basics. Diaphragm check and coil check next.

I have several of those screwdrivers somewhere :-)
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Old 07-15-2019, 02:12 PM   #8
six5monza
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Finally got around to checking the carbs last night. Apart from that one screw on the carb top everything looked really good, so just cleaned things up and put it all back together.

That one loose screw would indeed cause problems in all four carbs as it was definitely causing a vacuum leak. I'll know when I test ride it tonight if it worked. If the rain holds off here in Alabama...

Many, many thanks to those forum members who highlighted "the world's smallest O ring". No way in hell would I have spotted that, as the first one did indeed fall into the depths of the engine and had to be retrieved. A dab of grease on a finger tip worked for that delicate process!

Next is carb balance. I am wavering between building my own synch'ing tool or splurging and buying one. I may not use it again for another ten years :-)
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Old 07-15-2019, 05:46 PM   #9
six5monza
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She's Baaaaccckkkk!!! Rips right through the rev range now.
Very relieved that this was such a simple fix. One loose screw on a carb cap. Learned some stuff along the way too. I wish I could fix my broken Duc as easily...
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