Flat spot at 1/4 to 1/2 throttle?

[swbarnett]

I have a problem in that for the past 20,000k or so my bike has had a couple of issues when it comes to twisting the wrist. At between 1/4 and 1/2 throttle it dies until I open the throttle further. The second thing is that if I hold the throttle above 3/4 it splutters for a bit and at its worst won't go past about 8,000rpm (redline's about 11,500rpm).

The bike has Yoshi pipe that was put on about 70,000km ago. Nothing else was done to the bike at the time (i.e. no carb tuning or the like). I was told that this was not required and can attest that until recently this appears to have been correct.

BTW: The bike has just past 110,000km.

Any suggestions as to what might be going on and how to fix it? I've had a mechanic look at it. I'm just after a second opinion before I go ahead with their suggestion.

[Akzle]

its fucked. You know my offer.

[haydes55]

Sounds like carbs need a clean/balance. Could be anything from a sticky butterfly valve or slide or what ever you have in there. Or a partially blocked jet.

If the timing slipped, bearings are collapsing or anything else internal has fucked out, you would be having worse symptoms at a greater rev range.

Carb strip and clean, if that fails then look at electrical connections, could be due to at certain revs it rattles a loose connection enough to fuck an earth until the revs smooth out.

[skippa1]

Electrical.....maybe earthing issue, coils breaking down under load, plugs fucked, HT leads need replacing
Fuel.....crap in fuel, shitty in line filter, carbs shitty need clean and balance, shit in tank, water in tank or bowls

most unlikely it runs good for 70,000kms with the pipes then all of a sudden needs jetting

[swbarnett]

Sounds like carbs need a clean/balance. Could be anything from a sticky butterfly valve or slide or what ever you have in there. Or a partially blocked jet.
A mechanic has had a look and the carbs are clean as a whistle and working fine.


If the timing slipped, bearings are collapsing or anything else internal has fucked out, you would be having worse symptoms at a greater rev range.
That's what I thought. Other than the two niggly little problems it runs fine.


Carb strip and clean, if that fails then look at electrical connections, could be due to at certain revs it rattles a loose connection enough to fuck an earth until the revs smooth out.
I had the tank off last weenend and everything looked OK but I didn't specifically check the connections. I'll have another look this weekend.

I had another bike that used to cut out completely, then run for a while, then cut out etc. It turned out to be a worn throttle cable earthing on the cylinder.

[swbarnett]

Electrical.....maybe earthing issue, coils breaking down under load, plugs fucked, HT leads need replacing
Fuel.....crap in fuel, shitty in line filter, carbs shitty need clean and balance, shit in tank, water in tank or bowls
Plugs are brand new as of last weekend. Made no difference. Carbs, as above are evidently clean and working.

One thing I have noticed is that it runs better on Caltex than all the others (haven't tried Mobil yet). Runs worst on Gull.


most unlikely it runs good for 70,000kms with the pipes then all of a sudden needs jetting
That's what I was thinking. I even had the pipe repacked to return it to the original airflow. Didn't do anything noticeable but definitely sounds better than it did.

One thing I forgot to mention is that it runs perfectly without load. Revs like there's no tomorrow.

[unstuck]

Coil or coil packs? :2thumbsup

[buggerit]

split in carb boot?
oval emulsion tubes?

[swbarnett]

The really weird thing about this problem is that it only happens at higher speeds. I can take off from a standing start and gently progress through the throttle with no problem.

[Ribit]

http://www.kiwibiker.co.nz/forums/showthread.php/167405-Bike-won-t-run-GSXR750-K7

Beginning to sound like theres a common fault with this era zoom(less)zuki

[flashg]

My 2005 FZ1 ran like that on 95 octane. Put it onto 91 octane and it came good. Dealer said handbook says 91 only. He said there's been many problems with plugs (it stuffs them)many twins don't like it either. Other bikes I've owned love the stuff

[Drew]

Hmmm, till you said it happens when the speed was higher I was thinking battery voltage. But that usually presents at lower revs when the throttle is opened. Once the revs climb the load is lessened.

Got me fucked, take Akzels $5 and bag of chips.

[spanner spinner]

It will be worn needles and oval emulsion tubes, all Suzuki's with the type of carbs your bike has have this problem at some stage. I am surprised you made it this far they usually start giving problems around the 70,000k mark, maybe the pipe works with a slightly rich mixture better than the standard exhaust. You are talking wear in the 0.01mm range so it is hard to see with a eye-ometer.

[Drew]

Time for a set of flat slides! :banana:

You'll get better fuel economy than currently, but maybe not as good as when it was new.

Upside to the extra power...You get to listen to them go chikka chikka chikka at idle.

[swbarnett]

It will be worn needles and oval emulsion tubes, all Suzuki's with the type of carbs your bike has have this problem at some stage. I am surprised you made it this far they usually start giving problems around the 70,000k mark, maybe the pipe works with a slightly rich mixture better than the standard exhaust. You are talking wear in the 0.01mm range so it is hard to see with a eye-ometer.
Interesting. So the fix would be to replace the needles and emulsion tubes, yes?

[nzspokes]

It will be worn needles and oval emulsion tubes, all Suzuki's with the type of carbs your bike has have this problem at some stage. I am surprised you made it this far they usually start giving problems around the 70,000k mark, maybe the pipe works with a slightly rich mixture better than the standard exhaust. You are talking wear in the 0.01mm range so it is hard to see with a eye-ometer.

Bingo, we have a winner. :nya:

Exactly what I was thinking. But of course the the expert mechanic that looked at the carbs would have looked for that. ;)

[buggerit]

you might find this helpful, scroll down to photos etc
http://www.mtsac.edu/~cliff/storage/gs/understanding_carbs.pdf

[swbarnett]

Bingo, we have a winner. :nya:
I hope so. Does sound like that's probably it.


Exactly what I was thinking. But of course the the expert mechanic that looked at the carbs would have looked for that. ;)
Meh, we can't all know everything about every carb and I'm in no way qualified to judge.

[swbarnett]

you might find this helpful, scroll down to photos etc
http://www.mtsac.edu/~cliff/storage/gs/understanding_carbs.pdf
Thanks, I found that on the Gixxer forum (gotta love Google). Haven't had a change to read it yet.

[nzspokes]

I hope so. Does sound like that's probably it.


Meh, we can't all know everything about every carb and I'm in no way qualified to judge.
You said you had a mechanic look at it. Why did they not work it out? I would suggest a better mechanic. try Alec at Sme in Whitford. This is basic stuff.

Sent from my GT-I9300T using Tapatalk

[swbarnett]

Is anyone able to point out the parts that spanner spinner is talking about in the following diagram?

297993

[eelracing]

Is anyone able to point out the parts that spanner spinner is talking about in the following diagram?

Part Numbers #13 & #17

[unstuck]

Looks like 17 in that pic. :scratch:

[unstuck]

Part Numbers #13 & #17

Yeah, what he said. :lol::lol:

[nzspokes]

#16 and maybe the needle.

[unstuck]

#16 and maybe the needle.

Think you will find that 16 is the jet, 17 is the tube.;)

[spanner spinner]

Interesting. So the fix would be to replace the needles and emulsion tubes, yes?

yep new needles and emulsion tubes. Seen people spend months rejetting these carbs and they still run like shit replace the needles and emulsion tubes and there sorted.

[nzspokes]

Think you will find that 16 is the jet, 17 is the tube.;)

No, 19 is the jet. Middle bit is the emulsion tube. Bit on top is the guide. Thats the bit that wears on these. I believe some carbs its part of the emulsion tube. Normally they tap out.

[swbarnett]

yep new needles and emulsion tubes. Seen people spend months rejetting these carbs and they still run like shit replace the needles and emulsion tubes and there sorted.
Thanks.

So what's your take on the diagram I put up earlier? I seem to be getting some conflicting opinions as to exactly which parts these are and you seem to be the one with the answers...

[Akzle]

Thanks.

So what's your take on the diagram I put up earlier? I seem to be getting some conflicting opinions as to exactly which parts these are and you seem to be the one with the answers...


try Alec at Sme in Whitford.

. .

[unstuck]

16 needle jet, 19 main jet, 17 emulsion tube, 13 needle. :bleh:

[nzspokes]

16 needle jet, 19 main jet, 17 emulsion tube, 13 needle. :bleh:

Yes, now you've got it. Replace that lot.

[nzspokes]

. .

IKR. Some people love to spend money with below par mechanics or not work out problems and change things blindly. :facepalm:

[unstuck]

IKR. Some people love to spend money with below par mechanics or not work out problems and change things blindly. :facepalm:

So you have never changed a part that you thought was the problem, to find in fact it was only part of the problem?. Why are you not working for a formula one team.:not:

You sir are God.;)

[nzspokes]

So you have never changed a part that you thought was the problem, to find in fact it was only part of the problem?. Why are you not working for a formula one team.:not:

You sir are God.;)

I have indeed done that. But I have not charged others for faulty diagnosis.

[swbarnett]

Quick update: The problem is 100% fixed. Thanks to Spanner Spinner for the solution.

[swbarnett]

Quick update: The problem is 100% fixed. Thanks to Spanner Spinner for the solution.
A furhter update - about 10,000k later and the problem has returned. Any more suggestions?

[husaberg]

A furhter update - about 10,000k later and the problem has returned. Any more suggestions?

Order same parts..........bemuse how the quality of parts has diminished.

http://www.factorypro.com/Prod_Pages/prods14.html

You are lucky your needle jets are replaceable, as on some Keihins they are not.
Failing that make your own.

[nzspokes]

Order same parts..........bemuse how the quality of parts has diminished.

http://www.factorypro.com/Prod_Pages/prods14.html

You are lucky your needle jets are replaceable, as on some Keihins they are not.
Failing that make your own.

My thoughts exactly.

[swbarnett]

Order same parts..........bemuse how the quality of parts has diminished.
Are you saying what I think you're saying? That, although the original parts lasted a good 100,000km before crapping out the new ones are worn out after only a tenth of that?


http://www.factorypro.com/Prod_Pages/prods14.html
I take it these are a stronger part and shouldn't wear out so fast?


Failing that make your own.
If only. I wouldn't kno where to start and wouldn't have access to the necessary tools if I did.

Although I love the bike I'm starting to think it may be time to say good bye and trade it in for a VFR.

[nzspokes]

Are you saying what I think you're saying? That, although the original parts lasted a good 100,000km before crapping out the new ones are worn out after only a tenth of that?


I take it these are a stronger part and shouldn't wear out so fast?


If only. I wouldn't kno where to start and wouldn't have access to the necessary tools if I did.

Although I love the bike I'm starting to think it may be time to say good bye and trade it in for a VFR.

So when a bike needs servicing you give up on it?

A VFR will cost a lot more to service.

[husaberg]

Are you saying what I think you're saying? That, although the original parts lasted a good 100,000km before crapping out the new ones are worn out after only a tenth of that?.
That appears to be the case.


I take it these are a stronger part and shouldn't wear out so fast?.
I can't say for sure if they are, but why not investigate and google them.


If only. I wouldn't kno where to start and wouldn't have access to the necessary tools if I did.

Although I love the bike I'm starting to think it may be time to say good bye and trade it in for a VFR.
If you want to trade it in you will still need to fix it or get less money for it,wouldn't you?
If is the needle jet just worn, why not have a go at filling them up with bronze and re-drilling them. Realistically what do you have to lose.
I think you will find the cost will be less than a beer.
Last time you fixed it did you also replace the needles or not?

Last cr500 I had has similar issues, the jets are unable to be replaced, The simple bodge cure is a needle with a wider profile at the poont of excessive richness .........it doesn't "fix" the problem, but it does mask it pretty effectively.

[swbarnett]

So when a bike needs servicing you give up on it?
This is not just a matter of servicing. The last time I had this done it cost $800 by the time the labour was added on.


A VFR will cost a lot more to service.
Why would a VFR cost more to service? They're both four cylinder engines?
Even if it does, I doubt it sould be $800. For me that amounts to over $50 a week.

[swbarnett]

That appears to be the case.
Yeah, that's what I couldn't quite bring myself to believe.


I can't say for sure if they are, but why not investigate and google them.
Indeed I will.


If you want to trade it in you will still need to fix it or get less money for it,wouldn't you?
Of course. But I would hope that anything I would trade it for wouldn't have this problem. Especially as the VFR doesn't have carbs.


If is the needle jet just worn, why not have a go at filling them up with bronze and re-drilling them. Realistically what do you have to lose.
I think you will find the cost will be less than a beer.
This is way beyond what I'm prepared to attempt.


Last time you fixed it did you also replace the needles or not?
Both were replaced at the same time.

[husaberg]

Yeah, that's what I couldn't quite bring myself to believe.


Indeed I will.


Of course. But I would hope that anything I would trade it for wouldn't have this problem. Especially as the VFR doesn't have carbs.


This is way beyond what I'm prepared to attempt.


Both were replaced at the same time.


Ok just to replace the needle jets is a doodle. but while the carbs were open I bet they replaced plenty of other stuff likely did a tune and balanced the carbs etc.
Your time however is free.
Easy to do yourself too, bet there will even be a video on youtube.

If I remember rightly certainly, the older katana's were time consuming to get at stuff.

The VFR will likely cost more to service as it is a V. So two covers to take off etc etc.
think they have Vtech now too, as well don't they?

[nzspokes]

This is not just a matter of servicing. The last time I had this done it cost $800 by the time the labour was added on.


Why would a VFR cost more to service? They're both four cylinder engines?
Even if it does, I doubt it sould be $800. For me that amounts to over $50 a week.

Buy a manual and do it yourself. Its a carburetor not rocket science. I did a jet swap in 35 mins this morning. I reckon I could do the needles and seats in 3 beers or an hour. I did needles and seats on my Bandit, from memory parts were $70.

VFR is V-tec so more to check in a proper service. And more to pull off to get there.

[swbarnett]

If I remember rightly certainly, the older katana's were time consuming to get at stuff.
This is ceratinly what I was told was true for mine.


The VFR will likely cost more to service as it is a V. So two covers to take off etc etc.
think they have Vtech now too, as well don't they?

VFR is V-tec so more to check in a proper service. And more to pull off to get there.
I see what you mean. Certainly if I can get mine fixed properly I'd rather keep it.


Buy a manual and do it yourself. Its a carburetor not rocket science. I did a jet swap in 35 mins this morning. I reckon I could do the needles and seats in 3 beers or an hour. I did needles and seats on my Bandit, from memory parts were $70.
Honestly, carbs are just one step more than I'm prepared to tackle.


I'll have a word to the mechanic that did the job last time and see what they say given what you guys have told me. Honestly, it doesn't sound like they did the job right. We'll see what they say.

[unstuck]

This is ceratinly what I was told was true for mine.



I see what you mean. Certainly if I can get mine fixed properly I'd rather keep it.


Honestly, carbs are just one step more than I'm prepared to tackle.


I'll have a word to the mechanic that did the job last time and see what they say given what you guys have told me. Honestly, it doesn't sound like they did the job right. We'll see what they say.

See if you can find an old bike carb somewhere, and have a fiddle around with it a little. They are mostly not as scary as you may think. You can do eeeet.:niceone:

[husaberg]

This is ceratinly what I was told was true for mine.



I see what you mean. Certainly if I can get mine fixed properly I'd rather keep it.


Honestly, carbs are just one step more than I'm prepared to tackle.


I'll have a word to the mechanic that did the job last time and see what they say given what you guys have told me. Honestly, it doesn't sound like they did the job right. We'll see what they say.

I think they did it properly because it worked yes, just the parts are shite quality now not their fault.
Don't be scared of carbs There is f-all to f-up. they are pretty simple if you can do an oil and filter you can do them.

[nzspokes]

This is ceratinly what I was told was true for mine.



I see what you mean. Certainly if I can get mine fixed properly I'd rather keep it.


Honestly, carbs are just one step more than I'm prepared to tackle.


I'll have a word to the mechanic that did the job last time and see what they say given what you guys have told me. Honestly, it doesn't sound like they did the job right. We'll see what they say.

Well first yes I would talk to whoever did the job and ask why it failed so quickly.

If that goes nowhere ask on KB if somebody local can give you a hand to do the carbs. Pull them out yourself so whoever comes round just has to replace the parts. Easy job with the carbs off. Then give them beer.

Everybody wins.

[spanner spinner]

A furhter update - about 10,000k later and the problem has returned. Any more suggestions?

Are the carb slides chattering in the carb bodies? I would not expect the carb slides to be worn at this mileage but not impossible, if the slides are worn and chattering they put side load on the needles and cause them to wear vey rapidly as the needle is trying to centre the full load of the slide. this is easy to see as wear marks on the engine side of slides. thinking about it I have just had to replace slides on a triumph Bonneville a couple of months back that only had 30,000km on it due to slide wear and these use a similar carb slide design, worth checking. Also are you using a K&N filter? These can cause this type of carb to wear very rapidly. (bigger holes equal more air and power but also more dust getting through) What you need to check is part 11 on the following link http://www.partzilla.com/parts/search/Suzuki/Motorcycle/2003/GSX750F/CARBURETOR/parts.html easy to do just lift one of the outer carb tops and lift the slide out there should be NO!!!!! wear marks on the face of the slide and wear is to much.

[Vinz0r]

I had the same problem on a Bandit and fixed it with the factory-pro nickel plated emulsion tubes. Didn't want to bother with something that was going to wear in another 20,000 kms. As said above, slide chatter wears them very fast, which could be what has happened to you.
Most of the cost of having a dealer look at carbs is labour, they're not hard to work on so get out your tools and have a crack at it. New tubes and needles shouldn't cost much more than $100, which is a shit load cheaper than what your mechanic charged you.

[swbarnett]

Further update:

Talked to mechanic. They suggested new plugs and air filter as they're not the one that services it. I swapped those out and it's a lot better. I can get decent acceleration out of it now. I can get it to red line like it used to.

It sill has a problem in the same throttle area but now it's much reduced. Once the bike is fully warm it's only noticeable as a slight softening. If I sit in the problem area and add a little choke the problem goes away. Also, it's more noticeable when the engine is cold. If I understand correctly the fact that the addition of choke improves it means it's running lean, yes?

[Vinz0r]

Further update:

Talked to mechanic. They suggested new plugs and air filter as they're not the one that services it. I swapped those out and it's a lot better. I can get decent acceleration out of it now. I can get it to red line like it used to.

It sill has a problem in the same throttle area but now it's much reduced. Once the bike is fully warm it's only noticeable as a slight softening. If I sit in the problem area and add a little choke the problem goes away. Also, it's more noticeable when the engine is cold. If I understand correctly the fact that the addition of choke improves it means it's running lean, yes?

Yep sounds like it's a bit lean through that range, is it at around 4 - 6k rpm? Might need to shim your needles, there could be a flat spot coming off the pilots onto the mains as the needle lifts. This is good as it means your new emulsion tubes are probably ok! It runs rich when they're worn.