Hi, my FZR400 has been stoop whilst I tried to find a new generator case. Now I have one I've gone through and changed most of the easier things such as the chain which was old. Spark plugs, oils etc and the bike runs. But two of the downpipes aren't getting hot.

I doused a rag in water and squired some water on them and the two to the accelerator side were very hot causing the water to bubble off. The two to the clutch side just let the water there and slowly heated them until they evaporated.

I've check the plugs and they are fine. But otherwise I'm a little clueless as to what to try next. (And so is my dad hence why I'm here.)

Also, the leads for the broken two chambers come from different distributor packs.

Any help would be great. Thanks

Without a doubt this is a carburation fault.
As you state the running/non running cylinders are fed from the same coils.
It would be rare for two plug leads to go duff but not unknown.
Cut the ends back 5mm after removing the plug cap anyhow.

The bike has stood and the fuel evaporated whilst not being run.
This has deposited scale and debris in the jets.
You now need to remove the carbs and thoroughly go through every jet.
Be very careful if you remove the jet holder block....the brass nut shears off very easily.



Get a bit of old household flex and use a strand or two through the smaller jets
Soak in carb cleaner/acetone/thinners if you have any.

You need to be able to see cleanly through every jet !

Make sure the screwdriver fits the pilot jet perfectly....that's the main culprit for blocking.
Will it not pick up and run when past the idle circuit throttle position (about 2/3rd throttle upwards) ?

These bikes are very prone to jet/airway blockages if not started and warmed up regularly now there
is so much ethanol in modern fuels.

You should have been able to start it without the genny cover fitted...it's a dry casing.

When you take the airbox off; just start and rev it for a minute to check the throttle slides are all opening and not corroded shut.............rarer than hens teeth to have happened .

Check the numbers on the HT leads go to the correct plugs, they should be numbered, no1 is above the generator

Thanks guys, I've looked up block jets and it sounds about right. As it won't idle either without choke on. So I'll have a go at cleaning the jets out.

Thanks again :)

Whatever you do; DO NOT take the airbox off and leave it lying about for weeks.

The rubbers will be a barstool to get back on the carbs.

Make sure you have some quality tools to work on carbs.

This is not a job for a gravel drive and molegrips .

Good luck.

So I've cleaned out the carbs and the idling problems I was having have gone.
However, I still have two downpipes not getting hot.

Also when revved it's not returning to idle straight away. It's hovering just above.

Here's a video of the problem

https://vimeo.com/135599653

Any ideas about what the problem is? Thanks

Balance the carbs.

or you have an airleak

Just found out I have holes in my downpipes. Which is probably causing some issues.
Hopefully will be able to get them welded closed.

If not, does anyone know how to get downpipes that are EXUP compatible? The only ones I can find aren't.

There are a few threads about downpipes but there are no aftermarket exup pipes.