Running Problems - Identical problem on 2 bikes - 3ENx

[da_bad_macdaddy]

Hi Guys

I have the following bikes with the following mods:
1988 FZR400 3EN1 - Custom airbox with BIG air filter - race exhaust without EXUP
1989 FZR400 3EN2 - Custom airbox with BIG air filter - race exhaust without EXUP - custom Ram Air

Both bikes have the same problem: they wont rev above 8k. They just get there (very nicely in fact) and then sputter and wont go any higher.

I know the following are potential factors:
1. Carbs not jetted for air box and exhaust (most likely)
2. Battery not strong enough (not relevant as the 3EN2 has a brand new one)
3. Restrictor (dont think it is relevant as neither bike has a working speedo as they are for track use)
4. Dirty fuel lines (not relevant on the 3EN2 as it is all new lines, but the 3EN1 is not as clean)

Please let me know what you guys think. This is driving me nuts. I dont have spare jets to try and re-jet the carbs so I am hoping there is something I can do to get it working. I imagine the above mods are not unique - I guess everyone who rides their FZRs on track will have done similar mods.

PS. Both bikes have flat slide carbs - not the oval slides from the 1WG.

Cheers
D

[Taggyd]

its probably the restrictor, the 3en1's need to recieve a signal from a working speedo to reset, if you've just disconnected it that will most likely be your problem, the bike will limit itself and as its happening on both i'd say refit a speedo and give it a go! you will need an m-max box to remove the speedo!

taggy

[Evilchicken0]

It does sound like the restrictor but that should come in at 12,500 if the bike doesn't get the signal at 0mph/kmh

Do you have a set of CV carbs and a standard air box ???
The airbox and race exhaust will lean the mixture so that could also be a factor if you can put one of them back to standard then add the modifications one by one to see what makes the difference.

[da_bad_macdaddy]

Hi

Thanks for the feedback. I should have mentioned the bike only has a problem when driving - I can red line it when not in gear.

Yep, I think the carbs are CV - they are the standard ones on the 3EN2 from what I can make out. I have included a link to the pic of them below:
http://www.ragedigital.com/fzr/fzr600%2 ... attach.jpg" onclick="window.open(this.href);return false;

I tried to tape up the ait filter on the 3EN2 and it did allow it to get up to 15k, albeit not very smoothly so I dont think there is an electronic restrictor on that bike. On the 3EN1, I spoke to the guy I bought it from and he had (apparently) raced it without any problems - perhaps he is telling a load of lies, but the tyres do show they have been over right to the edge which I dont think is really likely at low revs.

I disconnected the rev counter because I know it feeds some info back into the ECU for restricting - but didnt experience any change in the machines rev limit. The speedo is connected on the 3EN2 but doesnt have a cable in it from the front wheel so hopefully that shouldnt impact it.

I havent been able to find any docs on the carbs or the settings. Does anyone know where I could find out the relevant info on how they should be set up and what jets I should see in them?

I have a couple of other (NON-desirable) solutions in mind:
1. Change the ECU with a 1WG Genesis one
2. Change the carbs for ones from the Genesis (which work perfectly with the carb/exhaust config)
3. Service my carbs and try to fix the problem that way

Thanks for the advice. Hopefully someone else has been thru the same problem and come out the other side without putting the bike on a bonfire...

D

[da_bad_macdaddy]

Sorry, didnt answer the question: the air box has been modified by taking the top off, putting a plate on the top of the bottom section with a hole in it to which a huge, free flow air filter is attached. On my Genesis this works perfectly and, following a dyno run, even impressed the dyno guy with its efficiency.

[Taggyd]

try running it with a speedo and see what happens!
as for the tyres wearing, i raced a restricted 3en1 and there was wear right to the edge of the tyre! it still makes 100mph+ even restricted and as the restrictor is for top speed, speed through corners isnt really going to hit the limit!though revs might, even out of gerrards was just hitting 6th onto the back straight! the only time you notice is in the drag down the start straight at mallory
taggy

[Evilchicken0]

The race pipe has no exup ... have you taken the servo off the bike ? Maybe the lack of the servo is upsetting the CDI.

it does sound like weak mixture though, you can try the genesis carbs as they're set for something like the airbox / filter / pipe that you running.

[da_bad_macdaddy]

Thanks guys. As soon as I have finished work I will get out in the garage to try some of the things you mention.

Any other suggestions, please feel free to post here.

Cheers
D

[Motorcycle Solutions]

Need to get them dyno'd and jetted for the bigger air intake... had same probs when i took the air filter out of the 3tj1 at oulton park rev'd to 8 and spluttered like hell...

[da_bad_macdaddy]

I think the carbs I have on the bike are pretty similar to the 3TJ carbs. Any ideas what the original & new jet sizes were?

Cheers
D