Fireblade flatspot

[nobeard]

I've a 97 Blade, which I believe is fitted with a Dynojet kit (Don't know which stage, I haven't opened up the carbs, plus I have zero experience of carb tuning - never seen the point, I've always left them standard).

The bike runs standard downpipes and silencer.

Symptoms:

Can't quote the exact rev range but there is a flatspot at roughly 5-6K.  Doesn't do it all the time.  Feels like it does it with wider throttle openings and/or in higher gears.  It's not horrendous, I'd just like to minimise it if possible.

So if you pull away in 1st, take it past 6K and change into 2nd, no flatspot, if you are going along in 2nd (or higher) and give it a wider throttle opening, it has a real 'pause' at 5-6K.  No misfire, no spluttering just a pause, gets through the 6k mark and then fires off.  Plus it absolutely flys along/sings when up in the rev range.

In every other respect it runs like a brand new bike - the fuelling is A1 - starting, idling, running along nicely at say 4k, smooth as you like all day.  I previously had the same model with double this mileage (this is 15.5K) and no flatspot, so I'm initially putting it down to the Dynojet, not a characteristic of the model.

Whilst I've not had the tank off, it's had plugs in the last 12 months and the whole bike is phenomenally clean - including what I can see inside the tank.  It's not old fuel or anything - I've done 450 miles on it in the last 2 weeks.  Plus I think any crap in the system would most likely manifest itself at idle.

Nothing I've seen indicates it's running massively rich - no soot in the tailpipe etc.  Doesn't smell either when you park it up hot.

 

Question is, to try and resolve it:

Is it possible that the main jets that are too big?

Or do the needles need moving slightly?   If so, moving them just one notch initially, would I raise the needle upwards in the diaphragm body or move them downwards?

I'm guessing the answer is 'play around and see', but based on the symptoms, is one more likely to be the cause than the others/be the first thing to try?

Whilst I've had plenty carbed bikes where I've had float bowls off for cleaning etc, and can identify all the inner components I really don't know the direction to go in to resolve the symptoms (and the less I touch Carbs the better - I hate getting to them/working on them).

Ta

 

 

[Gobert23]

Before adjusting anything, I'd be looking to drain, flush, drain again, clean, then fresh fuel and try.

You'll know that, the only real down-side with carb's (and modern fuel) is that they tend to glaze / gum up in the most inaccessible places.

Yup, I'd start with a clean of the internals and a balance. Should be bob-on.

[jaycee]

Just now, Gobert23 said:

This is your old bike. Were you aware of anything? Maybe just because it has been stood for so long.

 

[Gobert23]

Just now, jaycee said:

 

Ed-Zachary...

I was running is with a completely stock setup (OEM filter, headers, end-can, etc.) and dialled it in (roughly), before getting Paul (at DMC - My only trusted Honda tech' to look at it and dial it in*).

I hardly covered any miles (always a worry) and I was always caught between having it sitting with a dry tank (and drained carbs) or a brimmed / full tank.

@laney changed over to another OEM end-can, but no idea if there was any changes to the jetting?

 

*I might have a 'diary' of everything tucked away on a drive (old PC) somewhere, but there's not much to report on that one, short of 'a fuck tonne of cleaning materials' and receipts for 'Honda OEM parts'.

[spannerman]

I would say move the clips on needles a couple of grooves try it one way see if it's better if not try it the other, could be a lean or rich stumble

[lorenzo]

Pulling cleanly but without any real power is a sign of running lean, 5krpm then clearing up later sounds a lot like the needles want lifting by a clip, just to get a bit more fuel through in the midrange. 

[ydsparts]

If it is a bit hesistant when opening up, the bike is lean. Lift the needles one notch to richen it up, should do the trick.

[nobeard]

12 minutes ago, lorenzo said:

Pulling cleanly but without any real power is a sign of running lean, 5krpm then clearing up later sounds a lot like the needles want lifting by a clip, just to get a bit more fuel through in the midrange. 

Well. I am absolutely no expert (hence the ask), but the more I've looked into it, the more I'm thinking the same. 

I'll have a look at the plug colour out of interest, and maybe go down the cleaning route, but I'm inclined to try 1 clip lift.  Maybe it will just help the transition.

[ydsparts]

Plug colour will tell you nothing as modern unleaded makes them very hard to read.

[laney]

From memory, when I first brought it I had the carbs off for a clean and noticed it had got 120 mains in, I think standard is 116. The carbs were immaculate inside so all I did was a quick clean of the jets and new float bowl screws, and reset the air screws to standard specs.

I think that was when I changed the plugs, but in my opinion it doesn't need the fuel system flushing as such, as the longest it sat without being started and warmed up was only a couple weeks at the most in my ownership.

Have a mess, what's the worst that could happen!!

[firebeast]

Nobody has yet mentioned a few things,, how old is the kit? It was a long time ago but the dj kit needles may just have a crap design, plenty did, like 9r,srad600 etc,,lol, sorry. The needle taper could be causing it., or needle jet is getting a bit of wear, a well known old issue whichdj eventually fixed, but it can still happen with any brand and mileage.  Rev range is maybe as needle coming into play, too many issues potentially to say the easy  'lift the needle' quote.. Another one is plenty of the kits came with a drill bit to widen the slide and that can cause flutter on a lot of them at certain points..other thing to remember is 

You should read this,  plus maybe a few other folk who want to understand what each symptom may be telling you and the best ways to approach them.. This place is full of 'modders' who love to spend time sorting bikes, so can easily learn to tweak their carbs for the better,, it just takes time and patience and a bit of nice private road, tho tbh dj kits imho are usually just not the best design,, which dont help.   

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html 

It's a pity that dj flooded the UK market early on, which stopped factory Pro getting a fair crack of the whip, as Marc's kits have proper work and thought put into them and a comprehensive set of instructions to follow to get you the best from the bike and kit. He doesn't just say ' fit the kit, lift the needle a notch and your about bang on', which is bollocks anyway..he REALLY knows his shit..  I have seen a few so called dyno tuning places (not the well known established ones mind) just fit a kit word for word and move the needle a bit and that's it... 

[ydsparts]

Factory pro stuff is much better than the Dynojet tat. I have done a roaring trade in  selling ZXR and ZX7 stock carbs to swap with meddled ones. The dynojet stuff seems to wear out quickly as well with their chocolate needles. Even with a full system, etc , the stock stuff is usually fine with a little shim of the needle and a change of main jet. Marcs stuff is not cheap as the exchange rate and postage are crap but infinitely better.A worn needle jet will cause rich not lean running so won't cause hesitation or stuttering when winding it on to the transition. A worn needle jet will also mean the thing is mega rich on the pilot circuit as fuel is drawn up the emulsion tube with the vacuum. Have seen it a load on SRAD and ZX6 carbs which are notorious for it. Marc does replacement tubes for them as well.

[nobeard]

Well I took the plunge and raised the needles one clip.  But will be a good few days until I can test it though - needs a rebuild kit on the petcock. So that's on order.

[Thunderbolt]

17 hours ago, ydsparts said:

Factory pro stuff is much better than the Dynojet tat. I have done a roaring trade in  selling ZXR and ZX7 stock carbs to swap with meddled ones. The dynojet stuff seems to wear out quickly as well with their chocolate needles. Even with a full system, etc , the stock stuff is usually fine with a little shim of the needle and a change of main jet. Marcs stuff is not cheap as the exchange rate and postage are crap but infinitely better.A worn needle jet will cause rich not lean running so won't cause hesitation or stuttering when winding it on to the transition. A worn needle jet will also mean the thing is mega rich on the pilot circuit as fuel is drawn up the emulsion tube with the vacuum. Have seen it a load on SRAD and ZX6 carbs which are notorious for it. Marc does replacement tubes for them as well.

above is a picture of the non standard needle on the LDUGPz900r, complete with resin/tarnish.

@ydsparts factory pro or dynojet? There are no markings. It has 5 clip positions and is longer than standard.

[firebeast]

On 7/27/2020 at 3:42 PM, ydsparts said:

Factory pro stuff is much better than the Dynojet tat. I have done a roaring trade in  selling ZXR and ZX7 stock carbs to swap with meddled ones. The dynojet stuff seems to wear out quickly as well with their chocolate needles. Even with a full system, etc , the stock stuff is usually fine with a little shim of the needle and a change of main jet. Marcs stuff is not cheap as the exchange rate and postage are crap but infinitely better.A worn needle jet will cause rich not lean running so won't cause hesitation or stuttering when winding it on to the transition. A worn needle jet will also mean the thing is mega rich on the pilot circuit as fuel is drawn up the emulsion tube with the vacuum. Have seen it a load on SRAD and ZX6 carbs which are notorious for it. Marc does replacement tubes for them as well.

Try taking note of the bikes temp if it's still playing up(better or worse than it was before but not spot on) and do Full throttle as it the only way to really test things properly. Hopefully its cured it .. The main jet change is one where I have found a few swap out dj size then fit next Keihin or copy and wonder why it's not quite as expected..  Depends what the kit came with but if its 120 dj main it's likely a fair bit bigger than 120 keihin. Tbh, as with anything dj related, I would always say its worth a look inside to identify which brand of mains are in there. 

I got lucky on my F. Pro stuff price wise from starcycle in u.s... Bought ti needle kit for my 9r c good few years ago,but with identical needles and springs on the later F I bought, so swopped it over.. prices at the time were good, so got a shift kit as well,, which is well worth it.. He does an upgraded emulsion tube now which he says performs better, which would be nice, when the pound is worth double to a dollar 🙂

 

[ydsparts]

23 hours ago, Thunderbolt said:

above is a picture of the non standard needle on the LDUGPz900r, complete with resin/tarnish.

@ydsparts factory pro or dynojet? There are no markings. It has 5 clip positions and is longer than standard.

Probably Dynojet I would think as factory pro stuff over here is not common.

[Thunderbolt]

14 minutes ago, ydsparts said:

Probably Dynojet I would think as factory pro stuff over here is not common.

Thanks.

[firebeast]

Depending on the state of the main jets visually, from old memory, dj mains just have the number size stamped on them on the top face and its harder to read as smaller, with no etched band on the side,unlike Keihin or mikuni which have a logo.. F Pro usually use genuine Keihin but not always.. 

[ydsparts]

As above, the dynojet ones have smooth sides, the others all have a band round them.

[nobeard]

Quick update on the Blade.  I moved the needles from the 4th clip from the top to the 5th clip.

Took it for a ride last night and it was tens times worse.  Bloody awful.  Really bogging down, almost dangerous on an overtake. But again, flying past 7k. Tailpipe really sooty when checked.

So out in the sun at 7am this morning. Stripped down again. This time, set them on the 3rd clip from the top. Just tested it in the baking heat. Admittedly, only about 8 miles, but tried a variety of revs and throttle openings. Virtually perfect. Will give it a proper 100 mile try out early Saturday am, but as it stands, the best it has felt. Going richer definitely made it worse.....weird.  Air filter is like new etc. 

[firebeast]

 

5 hours ago, nobeard said:

Quick update on the Blade.  I moved the needles from the 4th clip from the top to the 5th clip.

Took it for a ride last night and it was tens times worse.  Bloody awful.  Really bogging down, almost dangerous on an overtake. But again, flying past 7k. Tailpipe really sooty when checked.

So out in the sun at 7am this morning. Stripped down again. This time, set them on the 3rd clip from the top. Just tested it in the baking heat. Admittedly, only about 8 miles, but tried a variety of revs and throttle openings. Virtually perfect. Will give it a proper 100 mile try out early Saturday am, but as it stands, the best it has felt. Going richer definitely made it worse.....weird.  Air filter is like new etc. 

If you went richer and it got a lot worse, thats sounding like the mains are too big. I did say if its got a 120 djmain it's not the same as a 120  Keihin, ie, it's richer again, so with a stockbike, if it's taking off after it clears its throat,I maybe wrong, but if you went down at least one size, read what the factory Pro guide says, it's MAIN jet first before anything,, focus on that and use his guide to finding the right size.. I may even have 118 and 115 dj mains possibly, which your welcome to try. Just throw me back the sizes that are left.. Happy having a look tomorrow.. 

Then try setting the needle up after.. You may find that the hole in the mid range is better straight away then just find the best setting, but only after getting the right main..  It may be better with 115 if its booing that badly, as its clearly too rich.. 

I haven't set up my aky racing line /evo system on my 9r fully yet as not been out all year, but Stephen rc45 when chatting about it, said on my 9f, he has finished lower than standard main size a few times, as the system is so good at optimizing the bike.. 😲

Edited July 31, 2020 by firebeast
Typo

[nobeard]

12 hours ago, firebeast said:

 

If you went richer and it got a lot worse, thats sounding like the mains are too big. I did say if its got a 120 djmain it's not the same as a 120  Keihin, ie, it's richer again, so with a stockbike, if it's taking off after it clears its throat,I maybe wrong, but if you went down at least one size, read what the factory Pro guide says, it's MAIN jet first before anything,, focus on that and use his guide to finding the right size.. I may even have 118 and 115 dj mains possibly, which your welcome to try. Just throw me back the sizes that are left.. Happy having a look tomorrow.. 

Then try setting the needle up after.. You may find that the hole in the mid range is better straight away then just find the best setting, but only after getting the right main..  It may be better with 115 if its booing that badly, as its clearly too rich.. 

I haven't set up my aky racing line /evo system on my 9r fully yet as not been out all year, but Stephen rc45 when chatting about it, said on my 9f, he has finished lower than standard main size a few times, as the system is so good at optimizing the bike.. 😲

I went out early this morning, 102 miles and really happy with the fuelling now. Tried every permutation of gear, throttle opening and some steep hills and it fuelled really well everywhere.

Appreciate the offer of the mains, but I'm happy to leave it as is for now.  What I'll likely do is keep an eye out for a full set of standard kit to turn it back to stock at some point.  But as I hate getting at and stripping carbs, I'm happy to leave it as is currently.

[firebeast]

No probs,   ya blade is pretty easy to work on tbh,  plenty of space, but I know tuning's not for everyone. Main test for me is a 5th gear roll on from nowt to flat out a few times, to get a feel for things, efore plenty of adjustments to fine tune it gradually.  It does usually take a lot of time tbh.