Wierd problem at top end

[Gazdaman]

Ok, I've raised this problem before.

On the MZ when flat out in top it'll lose all power and lurch forward as if you've suddenly let go of the throttle and applied a little front brake.

It'll do this, lurch forward, then go back to normal, and if you don't roll off a bit it'll carry on doing it.

Today it got worse. Which could be for a few things I've recently done:
Namely, fitting a sports exhaust, and running the tank onto reserve therefore tons of crap from the bottom of the tank in the carbs.

I think it's a fueling issue rather than a siezing issue, since it always goes back to normal.

Last time it was suggested it could be a breather hole issue, but my fuel cap is so loose and crap that can't be it. I think it must be a problem with either the carb, the fuel tap, the hose from the tank to the carb or possibly the air filter.

The carbs are getting a damn good clean tomorrow and a new air filter is on its way.

Any input?

Gaz

[Frost]

It could be the mixture its running. a mixture thats too rich can be very unhappy at high revs even though it starts well and runs well at low rev's.

Try adjusting the mixture, and make sure that the choke isnt sticking on.

[Gazdaman]

A too rich mixture would foul plugs though correct?

The plug looks as it should, not oily at all.

Gaz

[stinkwheel]

Yep, sounds like fuel starvation to me. Giving the fuel system a good clean out should see it right (don't forget to do the tap).

Have you considered fitting one of those big orange paper element fuel filters like they use in cars in the fuel line and doing away with the gauze filter in the tap? It will stop a lot more crap and you can see if it is blocked as they are transparent. Cost about 50p each.
____________________
“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.

[Gazdaman]

Good call, I know StinkWheel would hold the key.

TBH I've never had the fuel tap off so far so I don't know what's inside.

It'll get a damn good clean out tomorrow and I'll report back my findings.

Thanks guys.

Gaz

[stinkwheel]

[BlueNinja]

Take the carbs out, clean them properly, run the engine for a bit while dripping Redex into the choke, (mouth of carb) then replace the petrol filter.

If the carbs have diaphragms, check these for damage, (cracks), finally, if this doesnt work, bring the bike to a dyno center where they can check this kind of thing.

Best of luck

[Gazdaman]

There was a fair amount of crap in the sediment bit underneath the tap.

We pulled the hose out between the tap and the carb. That was fairly bunged up with crap aswell.

A full clean is going to take place when we've got a spare washer to put the fuel tap back on with. I doubt this stuff has ever been cleaned and hopefully this'll work some wonders for me.

Gaz

[stinkwheel]

I have never replaced a fuel tap sealing washer in my life. I would try it back on and only bother geting a new one if it leaks.
____________________
“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.

[Gazdaman]

After a day's work on the bike I've stripped the carb down into as many pieces as it goes into.

I've also had the fuel tap off, but it all seemed really clear.

The only thing I found that was a possible cause for the problem was a bit of fluff inside the main jet housing.

I removed that, and on first impressions the bike seems wierd. Top speed seems ever so slightly lower, but it seems more steady, I havn't had a chance to take it out for a proper run yet to see if it still does it.

New air filter comes next.

Gaz

[Gazdaman]

Went out for a rather eventfull ride today, the bike seems cured.

thanks for the input guys!!

think it must have just been the small bit of fluff/dirt in the main jet housing.

Gaz