XTZ 750 coughs and dies at full tilt??? WTF???????

Cylinder head, Barrel, Gearbox, Crank
CharlieGreger
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What Bike or Bikes Do You Own?: Yamaha XTZ 750 Super Tenere
Previously Owned Bikes: Yamaha XT 500
Yamaha XT 250
Honda XR 500 R
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Royal Enfield 350 Bullet
BMW R80 GS
Location: KZN Midlands South Africa
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XTZ 750 coughs and dies at full tilt??? WTF???????

Post by CharlieGreger »

Greetings all :wave:

I am having some trouble with my pony these days. And I am now at the point where i catch myself looking at the box of matches and petrol can more often :omg:
So here is the thing,

I have had this problem for a few months even before i started with adding new bits and pieces to it. I have just fitted new emulsion tubes from Kedo and replaced both the diaphragms(the DR650 is a perfect fit for these things, just plug and play!! :dance: ) I fitted a new exhaust from Wemoto, the marving jobbie. Too quiet for my liking but its what i could afford at the time. Feels restrictive though?

If i ride my bike like a normal bloke does, you know, keeps it clean, she pulls fine through all the gears and will happily cruise at 120kms all day. Still heavy on fuel though. and if i give it the beans and ride like a chop, to be fair i only do that on the dirt roads where there are very few people or traffic, its where i start having issues with my bike.

I will be, say in fourth gear, revs at about 6000rpm and my speed is about 140kms-150kms. at this point i have cranked the motor to get me here as fast as possible, the world is flashing past, scaring the cows etc. :fireball: then I change into 5th gear and the revs are higher and my speed is now approaching the limit, or should i say my limit that my nerves can handle which is about 180kms or so :hss:

Now i know some of you are probably sitting there saying... What a dick :DICKHEAD: .... and yes, I know its not ideal to be doing said speed in the dirt, but... well, I am an addict ok... there i said it!! :bong:

So i am winging it along at full tilt when the feking thing starts to play up on me. it coughs and splutters and surges back and forth like you do when you run out of fuel. So i ease off on the gas and after a short breather she is fine again, providing i keep the revs low and the speed down. I am back to riding at 100kms and there is no sign of a problem at all.

If i try to crank it back to full tit after its played up, the thing dies on me before i get past 160kms.


SO WHAT THE FUCK?????

I very seldom(read only twice a week or so) ride at full tit as there are only a few places that allow me the privelage to do so, so most of my time i am riding rather sedately. And now that the wife has started riding, I go even slower. It definitely feels lioke a fuel starvation, yet this only happens at full taps, not at a sensible speed. I have changed my rear sprocket to a 48 but that is just for more pull in the lower range.
I have checked the float heights and set them both equally to...errr... 11mm I think it was? I changed my emulsion tubes as they had done 30k and were due for a change as my fuel consumption was up. Now after fitting new ones i still have high consumption and still this full tilt issue( which is relatively new)
I rode up Sani pass in the drakensberg a few weeks back, and near the top, just when i needed the power to get me out ot the poo, she died on me and could barely breath at all. Getting to the top was a mission and a half!!

She has a new fuel pump, new fuel filters( one between the tank and pump and one between the pump and carbs) new emulsion tubes and needles, new diaphragms(both the old ones were shafted, one had a huge tear in it, surprised the bike ran at all. umm.... and a new Marving exhaust from wemoto. other thatn that she is as stock standard as she has always been.

I have tried all the things that i can think of, but i am still having troubles, so at the end of the day... fekin clueless at this point!! :dunno:

IF there is anyone out there..... anyone at all who may have a clue more than I, PLEASE share your pearls of wisdom!!! :pleasesir: :pleasesir: :sheep: :bouncing-boobs: :bouncing-boobs: :pleasesir:
ActionManMelb
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Re: XTZ 750 coughs and dies at full tilt??? WTF???????

Post by ActionManMelb »

You have classic fuel starvation problem.
Don't forget that for every cc. of fuel that leaves the tank, one cc. of air must enter to balance the pressures.

Make sure your tank cap vent is clear. Even try running with the cap loose.
"Don't worry," he said, "things could be worse ........."
So I stopped worrying and lo and behold, things did get worse!
CharlieGreger
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Posts: 82
Joined: Tue May 24, 2011 8:44 pm
What Bike or Bikes Do You Own?: Yamaha XTZ 750 Super Tenere
Previously Owned Bikes: Yamaha XT 500
Yamaha XT 250
Honda XR 500 R
Honda XR 200 R
Royal Enfield 350 Bullet
BMW R80 GS
Location: KZN Midlands South Africa
Contact:

XTZ 750 coughs and dies at full tilt??? WTF???????

Post by CharlieGreger »

Yep, I tried that already. The other day, on a similar stretch of road I was giving it the beans to see if it would run ok, and I got to 180kms with no hassles at all, the road ran out so I turned around to try it again, and it died on me before I hit the 160 mark. But for the most part it dies on me at full tilt, only occasionally will it run ok.
xtzrick
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What Bike or Bikes Do You Own?: '97 Yamaha XTZ660 Tenere, '79 Suzuki GS750
Previously Owned Bikes: Yamaha RS125, Suzuki GT125, Suzuki GT185, Honda CB250 G5,Kawasaki Z1000J, Kawasaki KL250, Yamaha TZR125, Yamaha XT600E
Location: Socialist Republic of S.Yorks.

Re: XTZ 750 coughs and dies at full tilt??? WTF???????

Post by xtzrick »

Have you checked the in tank filter Charlie?

& have you tried running without filters? Your new ones might not be big enough .

Rick
ActionManMelb
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Re: XTZ 750 coughs and dies at full tilt??? WTF???????

Post by ActionManMelb »

Rick's suggestion is a good one. Tank tap filters can block.

Next step would be a gravity flow test. Connect some tubing to the carb drain port and place a 1 litre container under the bike.
Open the carb bowl drain screw and time how long it takes to drain 500ml. Just a guess, but I would expect 500ml per minute as a guide.

About the rate you can drain your bladder. :omg:
"Don't worry," he said, "things could be worse ........."
So I stopped worrying and lo and behold, things did get worse!
CharlieGreger
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Posts: 82
Joined: Tue May 24, 2011 8:44 pm
What Bike or Bikes Do You Own?: Yamaha XTZ 750 Super Tenere
Previously Owned Bikes: Yamaha XT 500
Yamaha XT 250
Honda XR 500 R
Honda XR 200 R
Royal Enfield 350 Bullet
BMW R80 GS
Location: KZN Midlands South Africa
Contact:

Re: XTZ 750 coughs and dies at full tilt??? WTF???????

Post by CharlieGreger »

Well, I have just spent the evening having a poke about. I have checked the in tank filters.... clean as a whistle :yess:
I have replaced the fuel filter between the pump and the tank for a washable one. The paper filter one i took off looked ok so will see how it goes tomorrow.

the flow rate of fuel out the tank is good, about 700ml per minute. I will have to try the drain rate out the carbs another day as i dont feel lke going back into the freezing garage at the mo!!

but a question here, If i am having fuel starvation at full taps, how come my fuel consumption is still very high. 95% of my riding I do between 60kms- 100kms riding with the wife and up to about 120kms when riding with mates. and general riding on my own up to about 120kms or so. the best i have done on a tank is 550kms, i ran onto reserve on tuesday morning with only 290kms on the clock!!

Well fuck me!!!that is outrageous :omg: :wtf: :drugs: :bigyikes: :foot_tap:
xtzrick
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What Bike or Bikes Do You Own?: '97 Yamaha XTZ660 Tenere, '79 Suzuki GS750
Previously Owned Bikes: Yamaha RS125, Suzuki GT125, Suzuki GT185, Honda CB250 G5,Kawasaki Z1000J, Kawasaki KL250, Yamaha TZR125, Yamaha XT600E
Location: Socialist Republic of S.Yorks.

Re: XTZ 750 coughs and dies at full tilt??? WTF???????

Post by xtzrick »

CharlieGreger wrote:but a question here, If i am having fuel starvation at full taps, how come my fuel consumption is still very high.
It could be that fuel starvation is giving you less power, so you stay in a lower gear for longer while you are accelerating. Riding in a low gear gives higher fuel consumption.

Have you done spark plug "chops" to check their colour at mid to full throttle?

I know the emulsion tubes & needles are generaly considered to be the main cause of high fuel consumpsion on 750supertens (& 850 TDMs) but I've read consumpion was crap anyway 13.5-16.5kms/ltr (about 38-45mpg)
Your 550kms on 1 tank sounds fantastic for a 750 twin, perhaps I need some lessons or just open my throttle more :scratch:

Rick
CharlieGreger
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What Bike or Bikes Do You Own?: Yamaha XTZ 750 Super Tenere
Previously Owned Bikes: Yamaha XT 500
Yamaha XT 250
Honda XR 500 R
Honda XR 200 R
Royal Enfield 350 Bullet
BMW R80 GS
Location: KZN Midlands South Africa
Contact:

Re: XTZ 750 coughs and dies at full tilt??? WTF???????

Post by CharlieGreger »

xtzrick wrote:
CharlieGreger wrote:but a question here, If i am having fuel starvation at full taps, how come my fuel consumption is still very high.
It could be that fuel starvation is giving you less power, so you stay in a lower gear for longer while you are accelerating. Riding in a low gear gives higher fuel consumption.

Have you done spark plug "chops" to check their colour at mid to full throttle?


see here, the thing is, that while I ride the bike under normal conditions, it feels like it should. there are no hesitations or spluttering or the like, and I generally keep it clean. Yet still my fuel consumption is up. the 550kms I did on a tank was my trip down to the west coast and back over three weeks and 6000kms. I was averageing about 475kms to the tank. I once forgot to fill up and had to putt along at 60kms in 5th gear for about 90kms or so, when i filled the tank it took 30 litres, so i was literally on the dregs of the tank when i rolled into town. :riding: :hss: And I have yet to do the same mileage on a tank since then.

The bike doesnt feel like it needs to be kept in a lower gear for longer, which would make perfect sense if it did. But From the few changes I have made, I cant think of anything that will increase my fuel consumption to this extent. :dunno:

umm, what are plug chops??
CharlieGreger
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Posts: 82
Joined: Tue May 24, 2011 8:44 pm
What Bike or Bikes Do You Own?: Yamaha XTZ 750 Super Tenere
Previously Owned Bikes: Yamaha XT 500
Yamaha XT 250
Honda XR 500 R
Honda XR 200 R
Royal Enfield 350 Bullet
BMW R80 GS
Location: KZN Midlands South Africa
Contact:

Re: XTZ 750 coughs and dies at full tilt??? WTF???????

Post by CharlieGreger »

Just had a brain wave... albeit a small one... I will see if i can mount my point and shoot camera to my helmet and make a clip of said problem. I am not sure how the sound will be, wind noise etc, but might just work?? will give it a go and post it here for y'all to have a lookey looksee.

thanks for all the input! :thanks:
Teneroma
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Re: XTZ 750 coughs and dies at full tilt??? WTF???????

Post by Teneroma »

This will be good to see. i would expect only wind noise at full tilt.
Thanks
Damo
('99 XTZ660)
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