Occasional full-throttle hesitation

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tony.mon
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Re: Occasional full-throttle hesitation

Post by tony.mon »

sirch345 wrote: Sat Mar 07, 2020 8:03 pm

Excellent news :clap:
It's funny how quite often it's the simplest of things that can catch us out,

Chris.
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jchesshyre
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Re: Occasional full-throttle hesitation

Post by jchesshyre »

On a blast to the local farm shop yesterday I realised that although a new air filter has improved this problem, it's still slightly there. Little hesitation at 7000 rpm. Simce the new air filter did improve but not remove it, I'm thinking perhaps I'm a tad rich on the main jets. Will try going down a size to 172/175 and see how that is.
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Re: Occasional full-throttle hesitation

Post by jchesshyre »

Just to update on this... I've just put the bike back together after swapping my carbs with a spare set, because of a seized pilot jet. Same slides/diaphragms as before (although these were previously changed as part of trying to narrow down the hesitation), same (low mileage) needles, new slide springs, new silicone air-cut valve hoses, also trying 172F 175R main jets. Also changed to a different spare fuel tap, reinstated vacuum rather than manual operation and installed a new silicone vacuum hose.

I put new HT leads and caps and changed the coils for known good ones earlier this year.

Slight hesitation is still there, unchanged...

Next thing I'm going to try is Shell petrol instead of the Sainsbury's stuff I usually use like a cheapskate... Sounds silly but I should rule that out as a cause.

After that I guess I should look at cam chain wear (though no CCT adjustment needed for 60,000 miles suggests it's not bad as I said before) and maybe valve clearances?

Just to reiterate, the hesitation is only slight, occasional, and is only at 100% throttle and above 6k rpm, usually around about 7k. It's minor enough that some people would just live with it...but I am not one of those people...
tony.mon
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Re: Occasional full-throttle hesitation

Post by tony.mon »

Did you have a silicon vac hose fitted before?

I noticed a long while ago that using softer vac lines can cause a problem, as they can collapse and allow the vac at the tap diaphragm to decay, allowing the tap to close. Doesn't sound like your problem, as you mention having used a manual tap.
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jchesshyre
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Re: Occasional full-throttle hesitation

Post by jchesshyre »

I didn't, but yes as you say I've been running the tap manually for the last year or so, until yesterday.

Took it for a spin last night with Shell Super Unleaded in and couldn't get it to do the hesitation however hard I tried (sorry officer). But will do more testing before making conclusions and also try normal Premium from Shell or another non-supermarket garage. I can't believe this would be the cause though and had been running Sainsbury's for the last year or so precisely because I couldn't believe there was a big enough difference to matter...but...we'll see.
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sirch345
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Re: Occasional full-throttle hesitation

Post by sirch345 »

jchesshyre wrote: Tue Oct 27, 2020 9:08 am I didn't, but yes as you say I've been running the tap manually for the last year or so, until yesterday.

Took it for a spin last night with Shell Super Unleaded in and couldn't get it to do the hesitation however hard I tried (sorry officer). But will do more testing before making conclusions and also try normal Premium from Shell or another non-supermarket garage. I can't believe this would be the cause though and had been running Sainsbury's for the last year or so precisely because I couldn't believe there was a big enough difference to matter...but...we'll see.
I hope for you that is it, things like that can drive you nuts, or is it just me :)

Chris.
tony.mon
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Re: Occasional full-throttle hesitation

Post by tony.mon »

sirch345 wrote: Tue Oct 27, 2020 9:11 pm
jchesshyre wrote: Tue Oct 27, 2020 9:08 am I didn't, but yes as you say I've been running the tap manually for the last year or so, until yesterday.

Took it for a spin last night with Shell Super Unleaded in and couldn't get it to do the hesitation however hard I tried (sorry officer). But will do more testing before making conclusions and also try normal Premium from Shell or another non-supermarket garage. I can't believe this would be the cause though and had been running Sainsbury's for the last year or so precisely because I couldn't believe there was a big enough difference to matter...but...we'll see.
I hope for you that is it, things like that can drive you nuts, or is it just me :)

Chris.
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sirch345
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Re: Occasional full-throttle hesitation

Post by sirch345 »

tony.mon wrote: Wed Oct 28, 2020 12:06 am
sirch345 wrote: Tue Oct 27, 2020 9:11 pm
jchesshyre wrote: Tue Oct 27, 2020 9:08 am I didn't, but yes as you say I've been running the tap manually for the last year or so, until yesterday.

Took it for a spin last night with Shell Super Unleaded in and couldn't get it to do the hesitation however hard I tried (sorry officer). But will do more testing before making conclusions and also try normal Premium from Shell or another non-supermarket garage. I can't believe this would be the cause though and had been running Sainsbury's for the last year or so precisely because I couldn't believe there was a big enough difference to matter...but...we'll see.
I hope for you that is it, things like that can drive you nuts, or is it just me :)

Chris.
Yes, Chris, it's just you driving us nuts.
I love it when a plan comes together :wink: :lol:

Chris.
jchesshyre
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Re: Occasional full-throttle hesitation

Post by jchesshyre »

Well, what the HELL. I've now been through the tank of Shell V-Power and then two tanks of normal Shell, and try as I might I can't re-create the hesitation issue. Can this really be because of running Sainsbury's fuel? I knew there may be some differences in the composition and/or quality of the additive package added to supermarket fuels, but I didn't think it'd be enough to cause a running issue. Not only has the hesitation gone, but I think the engine is running slightly more smoothly as well.

The only other explanation is it's down to something I've changed when I swapped the carbs*, but I *did* get the hesitation when I rode the bike with these new carbs on, until after I'd filled up with the Shell fuel.

*i.e., the carbs themselves, the slide springs, the main jets from 175F 178R to 172F 175R, and the air-cut valve hoses.
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Re: Occasional full-throttle hesitation

Post by sirch345 »

jchesshyre wrote: Sun Nov 01, 2020 3:51 pm Well, what the HELL. I've now been through the tank of Shell V-Power and then two tanks of normal Shell, and try as I might I can't re-create the hesitation issue. Can this really be because of running Sainsbury's fuel? I knew there may be some differences in the composition and/or quality of the additive package added to supermarket fuels, but I didn't think it'd be enough to cause a running issue. Not only has the hesitation gone, but I think the engine is running slightly more smoothly as well.

The only other explanation is it's down to something I've changed when I swapped the carbs*, but I *did* get the hesitation when I rode the bike with these new carbs on, until after I'd filled up with the Shell fuel.

*i.e., the carbs themselves, the slide springs, the main jets from 175F 178R to 172F 175R, and the air-cut valve hoses.
That sounds promising :)

Chris.
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Re: Occasional full-throttle hesitation

Post by sirch345 »

jchesshyre wrote: Sun Nov 01, 2020 3:51 pm Well, what the HELL. I've now been through the tank of Shell V-Power and then two tanks of normal Shell, and try as I might I can't re-create the hesitation issue. Can this really be because of running Sainsbury's fuel? I knew there may be some differences in the composition and/or quality of the additive package added to supermarket fuels, but I didn't think it'd be enough to cause a running issue. Not only has the hesitation gone, but I think the engine is running slightly more smoothly as well.

The only other explanation is it's down to something I've changed when I swapped the carbs*, but I *did* get the hesitation when I rode the bike with these new carbs on, until after I'd filled up with the Shell fuel.

*i.e., the carbs themselves, the slide springs, the main jets from 175F 178R to 172F 175R, and the air-cut valve hoses.
I came across this while searching for information on renewing HT leads, as IIRC it was you who said it's possible to renew HT leads on the standard Firestorm/Superhawk HT coils having done so yourself.

I know this is nearly 12mths ago, but I'm interested to hear if the problem of the "Occasional full-throttle hesitation" ever returned :?:

Chris.
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Re: Occasional full-throttle hesitation

Post by jchesshyre »

Hi Chris, no, it didn't. Annoyingly I wasn't hugely scientific about it and didn't ensure I only changed one variable at a time, so I can't be totally sure what fixed it. I do know for sure that it runs better on non-supermarket fuel – if someone else told me this I'd be sceptical but there's absolutely no doubt.

If you (and anyone else) haven't done so, I HIGHLY recommend renewing the HT leads. It made a really really nice difference, like when you replace the spark plugs when they're overdue but possibly even more so. I used this https://www.gsparkplug.com/7mm-ht-ignit ... black.html – it's important to use wire core and not modern graphite core wire. At first I failed to replace the boot/seal on the coils properly and got a front cylinder misfire in the rain but quickly worked out what the issue was!
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Re: Occasional full-throttle hesitation

Post by sirch345 »

jchesshyre wrote: Sat Oct 23, 2021 1:06 pm Hi Chris, no, it didn't. Annoyingly I wasn't hugely scientific about it and didn't ensure I only changed one variable at a time, so I can't be totally sure what fixed it. I do know for sure that it runs better on non-supermarket fuel – if someone else told me this I'd be sceptical but there's absolutely no doubt.

If you (and anyone else) haven't done so, I HIGHLY recommend renewing the HT leads. It made a really really nice difference, like when you replace the spark plugs when they're overdue but possibly even more so. I used this https://www.gsparkplug.com/7mm-ht-ignit ... black.html – it's important to use wire core and not modern graphite core wire. At first I failed to replace the boot/seal on the coils properly and got a front cylinder misfire in the rain but quickly worked out what the issue was!
Many thanks for that information, including the link, that is very helpful :thumbup:

I'm guessing that one mitre of HT lead will be enough to do both coils? I appreciate the heads-up on the wire core and not the newer graphite core.
Does the old HT lead unscrew from the HT coil just like it does from a sparkplug cap :?:

Chris.
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Re: Occasional full-throttle hesitation

Post by jchesshyre »

It's a pleasure! Yes 1 m should definitely be more than enough. And yes, the attachment on the coil is a threaded spike like on the spark plug caps.

Just be very sure as I say to reassemble the seal properly where it enters the coil (and I guess a smear of dielectric grease wouldn't hurt either).

I found routing the front lead over the oil cooler quite fiddly but I think I was also being a bit lazy and not unbolting and lowering the oil cooler which I think would help.

Pay attention to the routing of the front lead and make detailed notes/photos as (again IIRC) the diagram in the manual doesn't show every detail and I think it needs to be just right – I'm mainly talking about towards the spark plug end rather than the coil end (you'll see what I mean when you do it).

Good luck and please do report back once you've done it :thumbup:
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sirch345
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Re: Occasional full-throttle hesitation

Post by sirch345 »

jchesshyre wrote: Sun Oct 24, 2021 10:54 pm It's a pleasure! Yes 1 m should definitely be more than enough. And yes, the attachment on the coil is a threaded spike like on the spark plug caps.

Just be very sure as I say to reassemble the seal properly where it enters the coil (and I guess a smear of dielectric grease wouldn't hurt either).

I found routing the front lead over the oil cooler quite fiddly but I think I was also being a bit lazy and not unbolting and lowering the oil cooler which I think would help.

Pay attention to the routing of the front lead and make detailed notes/photos as (again IIRC) the diagram in the manual doesn't show every detail and I think it needs to be just right – I'm mainly talking about towards the spark plug end rather than the coil end (you'll see what I mean when you do it).

Good luck and please do report back once you've done it :thumbup:
That's a great help :D

I usually take photo's as I go anyway on something like that, but I will make sure I take extra on this one :thumbup:

It will most likely be an over the winter job, but I will make sure I post up when I've done the job and tried the bike out on the road.

Many thanks for your detailed reply,

Chris.

PS. I should have said: I'm pleased to hear the problem of the "Occasional full-throttle hesitation" never returned :thumbup:
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