General EXUP question, and rough running problem

[Hedgetrimmer]

What is it about these gen 1s that they supposedly run so badly if you remove the EXUP? Is it the way the ignition timing is set up, the carburetion, a combination of such things? I mean, there used to be plenty of carb bikes that ran perfectly well without having any kind of valve in the exhaust system. Or is it that they just lose some of the low down oomph without it?


More than one reason I'm asking this. A little bit of history. On my 3rd gen 1, I occasionally used to get the 7k EXUP warning, but didn't notice any effect on performance when this happened. After a short while, the warning would just clear itself.


On the Hedgetrimmer, it turned out it never had an EXUP valve at all    Luke discovered this when he built the new bike for me, and took the foliage-lover off my hands. Now, that bike ran like crap at lower revs when I first got it. Glitchy, especially on small throttle adjustments, and most noticeable when coming off throttle in small increments in the rev range up to about 3k. After Ivanising funnily enough, there was hardly a problem, you could just notice it. Even Luke failed to spot it after Mike worked his magic.


Now, on the current bike, it's like it's running on 3 cylinders below 3k. The EXUP appears to be working fine, get the little whirring noise when I switch the ignition on, and no 7k warnings (btw, I did notice the extra grunt after the Hedgetrimmer, but I wouldn't call it a huge difference). When this first happened, the bike got a full service including carb balance and was fine for about 5-700 miles or so, then quickly went back to this poor low rev running. At first I got suspicious about the vacuum take-off fitting for the Scottoiler, as it is very loose, but taping it over with plumbers tape has made no difference, and anyway, I've been told since that it's such a tiny amount of difference this would make as to render it very unlikely (true?).


Something else - these are the same carbs that were on the Hedgetrimmer, in their Ivanised state, but as the manifolds were in nigh on perfect condition on this bike, but quite deeply cracked on the Hedgetrimmer, the ported ones were not transferred over (not noticed any adverse affect on performance due to this when all was running well). So these carbs probably have something like 40k miles on them in total.


The bike is booked in for a thorough service, this time also to include a valve clearance check, carb balance, EXUP service (Luke did this thoroughly about 15k miles ago), and I will be disconnecting the Scottoiler and putting a proper cap on the vacuum take-off - I've never found them to be any easier than just using chain lube or oil, even if this has nothing to do with the running problem.


All of this history has been explained to the chaps who will be doing the service, and they also seem to find it a little odd that after a service, things would be fine for a few hundred miles, and then rapidly deteriorate again. Can anybody enlighten me as to what might be going on here?

[Tommy250_2]

I can't answer all your questions, however, I recently acquired my first gen 1 and it was exup-less thanks to previous owner. It was lovely over 6000rpm but not so nice under that - particularly at steady throttle around 3000rpm (30mph in 2nd gear). I got an exup valve from a set of 1999 R1 headers. The bike then felt as good under 6000rpm as it did over 6000rpm. None of my previous bikes have had exup valves and so I was wasn't sure what to expect, but now I'm a convert! Bike pulls strongly from much lower in rev range.
Some choose to remove the exup... But as a newbie who has experienced a stock engine with and without an exup I can 100% say that the exup adds a huge amount to the character of the fazer.... It's a different,  and in my opinion, a much better bike with the exup valve present.

[unfazed]

Nick,
Check the Vacuum take off caps, they crack over time from age and are often the source of poor running low down of slow starting when very cold, the reason many do not think of them as a problem is because as vacuum increase it sucks them together and it feels fine at higher revs. I have had to replace them on numerous older Yams over the years. If you do need to go the replacement option go for 4 new ones as they are only about £12 to £15 for the 4.
The other cause may be due to a intermittent fault with the TPS again not to uncommon, (track wear within the unit), but will eventually throw up a 3k fault. This happened on my own one and me some time to figure out the problem and was a trial and error testing different items and it was when I tested the TPS it was on its way out, but it finally threw up the 3K fault the week I got a replacement. I bought a Suzuki on which is  half the price of the Yam one, but needs 2 wires swapped to get it to work on the Fazer 1000. I post a "How to modify" in the downloads section and it takes about 5 minutes to do.

[Hedgetrimmer]

Thanks for the suggestions Pat. I was beginning to wonder about the TPS. I'll put these points to the guys who will be servicing it since that's now booked, and get the bits on order, unless they discover something else that can be definitely identified as the problem.

[unfazed]

Forgot to mention, if you are getting an intermittent 7k exup fault it could be the servo motor giving trouble or stick cables, if the valve is ok.

[Hedgetrimmer]

Forgot to mention, if you are getting an intermittent 7k exup fault it could be the servo motor giving trouble or stick cables, if the valve is ok.

No, that was on a previous bike, this one's fine.

[AyJay]

When the EXUP opens, the ignition timing changes. I think this is what makes it run so badly when the EXUP isn't working properly. It isn't gas flow that makes it feel so rough, that just lowers the power at low revs, it's the ignition.


Also, just so's you know the TPS causes a surging feeling and it feels like the bike is momentarily cutting out, but in a gentle way. The TMAX 500 scooter's TPS is a straight swap. I actually bought a rusted up and knackered set of carbs off a chap for £20 just for that one 140 quid part. If only he knew....

[Hedgetrimmer]

Took it out for a run through town at traffic speeds today, keeping it below 3k. After a couple of miles, I pulled over to check the pipes, but they all seem to be getting good and hot, so don't think it's actually running on 3, although it was just a hand test. It's kind of "burbly" at those revs; hard to put it in words. A bit snatchy on throttle too. Seems to get a bit worse as it gets hotter too. It's not desperate, more just annoying cos I know it's not right. A visual inspection of the vacuum take-off caps shows them to be in pretty much perfect condition and all seated properly with the little clamps firmly in place. Think I'll get the workshop it's booked in with to check that all pilot jets etc are clear, cos that's what it seems to point to. If not, perhaps it is the TPS.


Blasted it up to the Hartside after that, and as soon as it's up towards 4k, everything's perfect.

[Falcon 269]

Any carb-related issue which gets worse when the motor is up to temp suggests rich fuelling.  A favourite cause in older Fazers is leakage past the float needle seat O-rings. 

Your symptoms indicate this could be the cause of your lower rpm misfire when hot.

[Hedgetrimmer]

Any carb-related issue which gets worse when the motor is up to temp suggests rich fuelling.  A favourite cause in older Fazers is leakage past the float needle seat O-rings. 

Your symptoms indicate this could be the cause of your lower rpm misfire when hot.

Thanks Mike. It's going in for a service tomorrow (not much of a fettler myself these days) and I'll discuss all these points with them. The mechanic at the place I'm taking it has a good reputation by all accounts, so hopefully he might be able to suss it. I would assume that if it is what you suggest, it's something that would  eventually get worse if not addressed?

[Falcon 269]

Yes, it will get worse.  It might just be one carb now but the others will follow in time and worst case, you'll get excess fuel leaking out of the overflows.

[Hedgetrimmer]

Service verdict: carbs were not seated properly on the manifolds, and carbs had been thrown way out of balance. Carbs themselves, everything in very good condition.


Time will tell, I guess.

[unfazed]

At least it was a simple fix. How would something like that happen?