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Breva 750 4000rpm flatspot

andyb

andyb

Cruisin' Guzzisti
Joined
May 11, 2010
Messages
185
Location
Farnsfield, UK
Appologies if this has already been covered, but I could not find any mention to it.

I have a 2006 Breva 750, about 10,000 mies now, which since I have had it at around 6000 miles has always had a flat spot at just below 4000rpm. It has been back to a local dealer who has set up the injectors (little improvement) and who told me that they are all like that! Apart from this rough spot the bike runs fine - but the problem is worse two up into a headwind, around 60mph in top gear. Below and above 4000rpm the bike pulls fine.

The bike is standard but spark plugs have been changed to Irridium and I have tried different fuel grades with no change.

Any ideas would be very helpful
Thanks

AndyB
 
Any ideas would be very helpful
Click to expand...

Yup.

Get used to it. Your dealer is right on this.
You can find the topic, searching for "Unsweet spot", and it's known. It may differ a little concerning the revs, but they all got it.
As it seems.
It's at an annoying rev. To me it's about 90 kmh, which is the "basic speed" on the main roads here.
There are two things to do about it; go faster or change gear. :mrgreen: There is a third, of course; slow down. At 3500 it spins like a Singer.
 
draidt said:
After market exhaust will improve it , say a set of Mistral's
Click to expand...


Maybe.
But you made me thinking of the ECU-update for the V7C. Wonder if it's appliable to the Brevas, and if it would affect the 4000rpm-spot..
If it's done we may have the so far non-existing warning-light issue into the bargain... :mrgreen:
 
Holt said:
Any ideas would be very helpful
Click to expand...

Yup.

Get used to it. Your dealer is right on this.
You can find the topic, searching for "Unsweet spot", and it's known. It may differ a little concerning the revs, but they all got it.
As it seems.
It's at an annoying rev. To me it's about 90 kmh, which is the "basic speed" on the main roads here.
There are two things to do about it; go faster or change gear. :mrgreen: There is a third, of course; slow down. At 3500 it spins like a Singer.
Click to expand...

Whoa, it depends. On my V7C, 4,000 rpm is the sweet spot, where the engine is smoothest. That's where I like to cruise. Above that the engine is still smooth, but there is the high rpm "buzz." Below 4K the engine isn't quite as smooth. Either way I haven't noticed a flat spot. It pulls fine all the way through.

If your problem is "two up in a headwind", well it could just be the placid nature of the engine. It's no 1200cc.

Joe
 
Thanks for replys.

Sounds like the V7C has different fueling then? So as Holt said, could the V7C ECU program be used on a Breva? I thought they were identical power units, but maybe not.

Draidt - thanks for the mentioning the exhausts - I was wondering if changing the header lengths might alter things.

Joe - I realise it is 'only a 750' but a 750cc bike should be able to hold 60mph with a bit of throttle response available, even into a headwind. When I was a lad a 750cc bike was king - and we toured Europe and North Africa on 500cc machines 2 up. The Breva seemed like a welcome change from heavier and heavier bikes with too much unuseable power. If it did not have this unsweet spot then the engine would be just right.

Did the earlier Brevas have carbs? And if so, did they have the same problem?
Could carbs replace the injectors?

My personal experience is that bike engines with carbs often have a smoother power delivery than with injectors - and it is possible to get carbs to replace the injectors for the BMW R1100 series! Certainly my '96 Triumph Speed Triple with carbs had a really smooth power delivery right throughout the rev range, not matched by later injected models.

Please keep coming with your thoughts as there is a lot of useful experience out there.

AndyB
 
There are no earlier Brevas. There is THE Breva.
There are earlier smallblocks though, many models and going back to 1972, using carburettors and displacements from 350 cc up. Then there are Nevadas and as the latest, the V7C, basically all the same.
And then there's a fat Breva. But that isn't a real Breva. :whistle:
 
Holt said:
And then there's a fat Breva. But that isn't a real Breva. :whistle:
Click to expand...


Hey, them's fightin words them is.... :D

FWIW, The minister says that if she rides her Nevada at just under 100Ks it isn't very happy, and her solution is to go slower..... :roll:
 
Why do girls do that. My partner likes to slow down to let cars in the left lane merge in front of her. And she slows down on the engine, not the brake. So no brake lights to help me notice what she is doing :eek:hmy: not fun.

I’m riding her 750 at the moment with my Sport in the shop. I’ll check but I think she is quite good at 4,000rpm, just a bit bumpy on trailing throttle like most injected bikes. I'm usually riding closer to 5,000 than 4,000 (2004 - 5 speed)
 
Andy, you are so right. When I was young a Honda 360cc was plenty of power. Before the 750 I had a BMW 500cc (26hp!) and happily toured with that. I didn't mean to slight the Guzzi 750. It does have all the power one needs. It's just that two up, in a headwind, you might not have the neck-snapping acceleration you get out of some machines.

The Guzzi 750 bikes are an excellent blend of easy power and light weight, in a durable time-tested design. It won't perform like a 4 cylinder sport bike with a 12,000 rpm redline, but it won't give you the maintenance headaches of those bikes either.

Joe,
 
I am amazed by the replies above.
If Holt is right amd all the Brevas have this problem of an 'unsweet spot' at 4000rpm - then surely there must be a tweak to sort it out?
Otherwisde my solution will not be to ride faster, slower or change gear. It will be to sell the bike.
AndyB
 
Sell the bike? :eek: how bad is yours?

I was checking out my 750. I guess it’s flat, but I can’t really notice a difference and certainly wouldn’t call it a defect or even unsweet. I can get ~4,000 at 80km and 100km. Roll on to full throttle and it is like a ruber band, she winds up gets ready and goes. She does start to pull much more by 5,000 but it’s not like I have to change down gears to pass cars and I tend to set up my passing attempts a bit anyhow.

Sure it’s not like riding a 600cc sports bike, but the 750 isn’t like a 600cc sports bike :lol: It’s been a while but feels about the same as a 650 monster (I have not ridden the latest one) or a 883 Sportster (obviously handles much better than that) In-line 4 600's need to high up in the rev range to get them to accelerate with me siting on them.

The power specs are not spectacular for the 750 and given the numbers I think she performs REALLY well. I'm 115kg, my partner is 80kg and the 750 even goes ok with the 2 of us on her. Don’t even notice headwinds. But to be fair I do notice it’s 2 up, on the 1200 my partner hardly makes a difference, but she still goes quite well. I think youtube has a vid by Guzzimoma touring around the states 2 up.

I must admit that while I do enjoy the power of my 1200Sport I’m really enjoying the 750 so much. Nimble little bike. Reminds me of my 1st real road bike, a VTR 250, except the 750 goes faster than 145km/h overtakes much better and the VTR wouldn’t do over 120km/h 2-up.

Every time I ride the 750 Breva I wish I had the money for a V7 Café
 
andyb

Gee, selling the bike because of a bit of a grumble when operating at a particular rev is a bit drastic! No way would I describe the 750 engine as not being "right", far from it it's an absolute gem and I love riding the Minister's Nevada for all the same reasons as Mal. Sure it's got a bit of an unhappy spot but lots of engines have similar traits. However we all have different expectations I suppose.

A Power Commander III does change the power delivery of the engine dramatically if you want to play around.
 
andyb said:
I am amazed by the replies above.
If Holt is right amd all the Brevas have this problem of an 'unsweet spot' at 4000rpm - then surely there must be a tweak to sort it out?
Otherwisde my solution will not be to ride faster, slower or change gear. It will be to sell the bike.
AndyB
Click to expand...

At least it's my impression that I'm right.
But it is NOT a problem. It's noticable. That's what it is. I've had mine for 60000 kms by now, and have absolutely no intentions of changing to anything else, because there are nothing better out there.

I'm wondering if your Breva is set up right. TPS? Throttle balancing? Plug gap 0,65 mm? How did your dealer "adjust" the injectors? AFAK there's nothing to adjust, if only they are seated right. Using a tool like the Axone, can give you a message if they works or not, that's it.
 
Holt is right! I looked at six dynamometer charts for the Breva or V7C and they do show either a dip or a flat spot right at 4k! I never noticed it before, certainly not when riding, but if you examine the charts with an eye for 4k rpm it's there. Some diagrams show it as tiny, hardly there at all, while it's pronounced on other graphs.

It looks like many people fixed it with performance modifications. The dynamometer charts are in the Files section of http://autos.groups.yahoo.com/group/MG_750/

It's really odd. I don't notice it when riding, but the numbers don't lie. Something to think about.

Joe
 
So I’m still zapping about on the 750 and to be totally honest I just don’t have any issues at 4,000 rpm. Was riding in top gear 100km/h uphill, rolled on and accelerated away nicely. If it wasn’t for the discussion I just wouldn’t notice it as an issue, although she does spin really nicely up around the red line too ;)

Andy B the small block Guzzi is just a different bike to ride than something like an R1100 and if the speed triple was anything like my RS 955 both of those have quite a bit more HP than the Breva. Yes a 750 WAS a big bike (I still get in trouble with my dad referring to our GS500 as a little bike) but hop on one of those classics now and the acceleration (and brakes) are nothing like a modern machine.

While there are “faster” bikes I can’t think of anything “better” than a 750 Guzzi for doing everything, otherwise I’d own something else :) But perhaps an 1100 or 1200 would just be more what you are after in a bike.
 
I have to agree with you Mal. When I was bike shopping, I was drawn by the Suzuki GS500 for which the dealer was offering some pretty competitive deals. The same dealer also had this 750 Breva that had a lot of options fitted including panniers and a screen.

I test rode the Suzuki and the Breva back to back, and found the Moto Guzzi a much more refined ride with similar weight and performance. Whether I'd buy a new one at the prices they ask is another matter, but it was better enough than a new Suzuki GS500 for the same price even with 40,000+ km on it to take my cash. The Suzuki had an off idle fuelling problem that meant you had to be very judicious opening the throttle at low to medium revs. The Moto Guzzi just tractored on.

As for the 4000RPM flat spot. Not this one really. Anything over 2000RPM works if you must. Anything over 3000RPM works better and anything over 5000RPM works better again. Not a powerhouse, but it's all where I use it.

Note of course that mine is an Australian delivered model. Lots of bikes have deliberately induced flat spots to pass drive by noise tests or RPM specific emissions tests (Suzuki SV650 and SV1000 is a good example). Sometimes these are country specific and it could well be that US spec models have a flat spot deliberately arranged to help pass an emissions test.
 
Problem solved - sold it.

I sold it to the dealer who had previously set up the injectors and told me thet 'they all have a flat spot at 4000rpm'. Shame really, but I felt it spoilt the bike - the engine was otherwise so good.

My every day bike is a 1995 R80R BMW boxer with carbs which I have had from new, and that has a similar power output to the Breva, so I am used to 50hp bikes. I rather hoped that the Breva might replace the BMW (lighter, better fuel ecconomy, better brakes and handling) but it was not to be. I will sometime have a go on a V7 though.........

Bye for now
AndyB
 
The flat spot is really bike specific. On some it's noticable, but on others it's hardly there at all. On my V7C it's fine. In fact 4,000 rpm is my bike's sweet spot; where the engine is smoothest for cruising.

Joe
 
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