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VidalBaboon

Original Poster:

9,073 posts

100 months

[news] 
Monday 14th May 2012 quote quote all
Help me diagnose my poorly 7R.

Poor running below 4krpm, wind the throttle on and it gets worse, to the point of cutting out. It then won't start for a few minutes (wet plugs at a guess). Once it fires up, you have to hold the throttle at a certain position till it revs cleanly through.

Once this has happened, you have to clutch it up past 4krpm and it runs fine.

I pulled my carbs apart hoping it was something simple, but nothing obvious apart from Dynojet needles and ever so slightly ovaled needle jets. I put the needles on their leanest settings but no joy, so I took the carbs off and put a second hand standard set on. It's still doing the same thing.

Assuming I've ruled out fuelling by fitting a different set of carbs, next up is the ignition system. I've got a pulse pick up coil, loom and CDI waiting to be trialled.

Am I missing anything glaringly obvious? Perhaps check the reg/rec- see if it's giving the CDI enough juice at low revs, split inlet rubbers (they did look alright, but it was only by glancing at them - gets a bit tedious taking the carbs off every 5 minutes)


Please help!

Yazza54

13,207 posts

66 months

[news] 
Monday 14th May 2012 quote quote all
Have you changed anything since it last ran ok?

Would definitely be checking rubbers

VidalBaboon

Original Poster:

9,073 posts

100 months

[news] 
Monday 14th May 2012 quote quote all
Nobody likes a split rubber. They looked good to me when I pulled them off, but will check again.

Shirley a split rubber would cause the fueling to get progressively worse as the vacuum increases with raised engine revolutions??

k15tox

1,680 posts

66 months

[news] 
Monday 14th May 2012 quote quote all
Any of the vacuum pipes on the carbs kinked?

I had similar on my CBR but above 7k.

Yazza54

13,207 posts

66 months

[news] 
Monday 14th May 2012 quote quote all
VidalBaboon said:
Nobody likes a split rubber. They looked good to me when I pulled them off, but will check again.

Shirley a split rubber would cause the fueling to get progressively worse as the vacuum increases with raised engine revolutions??
Surging can make a motor run all sorts of rough, do the revs hang before decreasing when you let off the throttle?

Have you rejetted after fitting your new exhaust system?

Have you done anything to the breathers?
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VidalBaboon

Original Poster:

9,073 posts

100 months

[news] 
Monday 14th May 2012 quote quote all
No I don't think so, I did a float bowl mod (equalised the pressure between float bowl vent and airbox) but it ran exactly the same. So I've decided to go from square one and put it all back to standard.

VidalBaboon

Original Poster:

9,073 posts

100 months

[news] 
Monday 14th May 2012 quote quote all
Yazza54 said:
VidalBaboon said:
Nobody likes a split rubber. They looked good to me when I pulled them off, but will check again.

Shirley a split rubber would cause the fueling to get progressively worse as the vacuum increases with raised engine revolutions??
Surging can make a motor run all sorts of rough, do the revs hang before decreasing when you let off the throttle?

Have you rejetted after fitting your new exhaust system?

Have you done anything to the breathers?
No they don't hang, thinking about it I have noticed a delay when blipping the throttle on downchanges (8-10k), there's sort of a split second delay which isn't apparent at low revs (5-8k).

The bike runs huge mains to compensate for the air recirc system on the exhaust. The bike was originally running mains suitable for a snazzy system but it made no difference having Keihin 180 mains or Dynojet 132 mains. Having the jets slightly out would never make it run this bad anyway, flatspot yes, but not this bad.





Edited by VidalBaboon on Monday 14th May 22:08

VidalBaboon

Original Poster:

9,073 posts

100 months

[news] 
Monday 14th May 2012 quote quote all
All 4 plugs are fouling, assuming I've ruled out any fuelling issue wih swapping the modded carbs for a standard set (the guy that's put the carbs in used to be involved with racing 7Rs in the 90s, so guessing he has a better idea of well set up carbs than me)

the only other thing that affects all 4 cylinders is the ignition, or as you say, a pesky air leak.

snarfy

116 posts

141 months

[news] 
Monday 14th May 2012 quote quote all
Have you tried new ht leads and fresh sparkplugs ? Had an issue like this but car related in an old vw. Low revs had a horrible vibration with no real pickup that seemed to get worse as you put your foot. High revs were much better but that could simply have been masking the issue. Checked all sorts and, after speaking to my local mechanic he recommended the above.
What was really odd was that there was no gradual deterioration. One minute it was fine and the next it was st.

VidalBaboon

Original Poster:

9,073 posts

100 months

[news] 
Monday 14th May 2012 quote quote all
Tried a different set of spark plugs. Not bothered checking the continuity of the HT leads and plug caps yet as it's affecting all 4 cylinders, not just one or two (2 as it's got twin coil packs).

Yazza54

13,207 posts

66 months

[news] 
Monday 14th May 2012 quote quote all
Fouling plugs screams bad mixture to me. But the bad mixture could either be the carbs themselves or an air leak.

If all plugs are fouling but firing, it has to be something effective all four like you say, the leaves you with searching for air leaks or trying a spare CDI. I'd bet on it being a carb jetting/air leak issue though.



Edited by Yazza54 on Monday 14th May 22:17

Yazza54

13,207 posts

66 months

[news] 
Monday 14th May 2012 quote quote all
VidalBaboon said:
Yazza54 said:
VidalBaboon said:
Nobody likes a split rubber. They looked good to me when I pulled them off, but will check again.

Shirley a split rubber would cause the fueling to get progressively worse as the vacuum increases with raised engine revolutions??
Surging can make a motor run all sorts of rough, do the revs hang before decreasing when you let off the throttle?

Have you rejetted after fitting your new exhaust system?

Have you done anything to the breathers?
No they don't hang, thinking about it I have noticed a delay when blipping the throttle on downchanges (8-10k), there's sort of a split second delay which isn't apparent at low revs (5-8k).

The bike runs huge mains to compensate for the air recirc system on the exhaust. The bike was originally running mains suitable for a snazzy system but it made no difference having Keihin 180 mains or Dynojet 132 mains. Having the jets slightly out would never make it run this bad anyway, flatspot yes, but not this bad.





Edited by VidalBaboon on Monday 14th May 22:08
That's a bloody huge difference in jets not to make any difference to the running! Is it on 180 or 132 now?

VidalBaboon

Original Poster:

9,073 posts

100 months

[news] 
Monday 14th May 2012 quote quote all
Dynojet sizes are different to Keihin, and it has the emissions ste back on to lean the mixture out (somehow, black magic I assume).

You can (apparently) run an aftermarket system on standard jetting without any 'major' problems, I certainly had no issue swapping between standard and open can on the last one. If it was a jetting issue, it would have been cured by fitting the new exhaust.


Edited by VidalBaboon on Monday 14th May 22:23

Fleegle

12,560 posts

61 months

[news] 
Monday 14th May 2012 quote quote all
Does it have an inline fuel filter?

If so, when was it last changed?

Yazza54

13,207 posts

66 months

[news] 
Monday 14th May 2012 quote quote all
VidalBaboon said:
Yazza54 said:
VidalBaboon said:
Yazza54 said:
VidalBaboon said:
Nobody likes a split rubber. They looked good to me when I pulled them off, but will check again.

Shirley a split rubber would cause the fueling to get progressively worse as the vacuum increases with raised engine revolutions??
Surging can make a motor run all sorts of rough, do the revs hang before decreasing when you let off the throttle?

Have you rejetted after fitting your new exhaust system?

Have you done anything to the breathers?
No they don't hang, thinking about it I have noticed a delay when blipping the throttle on downchanges (8-10k), there's sort of a split second delay which isn't apparent at low revs (5-8k).

The bike runs huge mains to compensate for the air recirc system on the exhaust. The bike was originally running mains suitable for a snazzy system but it made no difference having Keihin 180 mains or Dynojet 132 mains. Having the jets slightly out would never make it run this bad anyway, flatspot yes, but not this bad.





Edited by VidalBaboon on Monday 14th May 22:08
That's a bloody huge difference in jets not to make any difference to the running! Is it on 180 or 132 now?
Dynojet sizes are different to Keihin
Oh good haha. Still, which ones?

VidalBaboon

Original Poster:

9,073 posts

100 months

[news] 
Monday 14th May 2012 quote quote all
Fleegle said:
Does it have an inline fuel filter?

If so, when was it last changed?
It's not starving of fuel. Filter looks good, no crud in the tank either.

VidalBaboon

Original Poster:

9,073 posts

100 months

[news] 
Monday 14th May 2012 quote quote all
Yazza54 said:
Oh good haha. Still, which ones?
It's running standard carbs with the emissions stuff back on. I have tried to put it back as standard as possible to fault find.

Yazza54

13,207 posts

66 months

[news] 
Monday 14th May 2012 quote quote all
VidalBaboon said:
No I don't think so, I did a float bowl mod (equalised the pressure between float bowl vent and airbox) but it ran exactly the same. So I've decided to go from square one and put it all back to standard.
Reet, read this (if you havent already) http://homepage.ntlworld.com/webzxr/zxr750r/Featur...

With your mod it sounds like your jetting may now be too rich which would explain the plugs fouling and an unwillingness to rev until it clears its throat.

Yazza54

13,207 posts

66 months

[news] 
Monday 14th May 2012 quote quote all
VidalBaboon said:
Yazza54 said:
Oh good haha. Still, which ones?
It's running standard carbs with the emissions stuff back on. I have tried to put it back as standard as possible to fault find.
And it's no better?

CQ8

329 posts

112 months

[news] 
Monday 14th May 2012 quote quote all
Has it always done this since you bought it or is it a new problem?

I thought it went pretty well when I had a go, apart from this issue causing it to cut out on me, so my money is on the electrical/CDI side (I'm no mechanic though biggrin)

I still think it will be a good bike once this is sorted, it's just a case of finding the problem. Is it worth putting back to standard if none of the mods you have done have effected it?

Edited by CQ8 on Monday 14th May 22:39

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