Can I use Dynojet needles with standard main jets?

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sisumi
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Can I use Dynojet needles with standard main jets?

Post by sisumi »

First post! I've been amazed at all the advice available on here. Pretty much any question I had so far has been answered before. But I can't find an answer to this one, so I'm hoping someone might be able to help.

I've had my Storm for a few months, and I'm trying to fix the poor low speed running. When I purchased it, it had standard exhausts, but looking back at its MOT history, it consistently had an advisory on loud exhausts. So clearly the originals were put back on for the sale (they're immaculate). The problem is, at low throttle openings, it was quite difficult to ride, was 'carb farting' quite a bit, and was particularly rough around town. Beyond 4000 rpm, she cleared her throat and took off. I had a look at the filter, and could see it's running a K&N, then I took a look inside the carbs and it's using a dynojet kit with 190 mains and 45 pilots. So running the upper end of main jets, with standard pilots.

I'm not really chasing top end performance and would be happy lose some top end for a smoother low and mid range, so I want to take it back to standard carburation. I have a standard filter, a 178/175 set of main jets, but I don't have a set of standard needles. So can I use the existing dynojets? I'm not sure if the dynojet needle is basically the same, except for the ability to set the needle height.

Thanks!
Simon
tony.mon
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Re: Can I use Dynojet needles with standard main jets?

Post by tony.mon »

You should be fine using the dynojet needles.
And welcome!
It's not falling off, it's an upgrade opportunity.
sisumi
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Re: Can I use Dynojet needles with standard main jets?

Post by sisumi »

Thanks! I'll give them a go.
Harveyz
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Re: Can I use Dynojet needles with standard main jets?

Post by Harveyz »

I'm struggling with exactly the same issue - had a dynojet kit (190 mains /48 pilot) on it and some LexTek pipes which were really loud - stuttered and surged between 3000 and 4000 was a nightmare to ride - so I Fitted Delkovic cans, jetted down from 190's to 178 FR and 180 R plus it had 48 pilots - more importantly has your CV slides got three holes - if so block up the one which was drilled when the dynoject kit was fitted - set the TPS at 500 ohms. I tried a a base fuel screws 2 1/4 Fr and 2 1/2 R. Only thing I didn't change was the Dynojet Needles which were set on the 4th notch

Runs much better - smooth as silk above 3000rpm - but still struggling if the rev drop to 2,000 its stutters until it get to 3,000 and we're away - my though is it can't be the main jets of needle as it below 3,000rpm. - it's got to be either pilot jet or fuel screw.

My next try will be back to basics 175 FR, 178 R, pilot 48 and play with the fuel screw setting

Keep me posted how you get on
sisumi
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Re: Can I use Dynojet needles with standard main jets?

Post by sisumi »

So an update from me. The bike now runs perfectly well, in fact a transformation over the jerky on/off throttle I was having before. It's my first v-twin after a load of fours, and I wasn't sure what to really expect - but after watching a few on-bike Youtube vids, it was clear they weren't having the low speed issues I was having. It now picks up smoothly from low revs and just keeps pulling.

So in total, I've:
Re-jetted to 178/175/45 (2.5 turns and 2.75 turns on the fuel screws)
Kept the dynojet needles (on the same clip position)
Replaced float valves and o-rings throughout carbs
Filled the third hole in the slide with epoxy
Replaced the carb boots (these had the 'restrictor' plate, but I fitted anyway, not sure how much difference they make)
Fitted standard filter
Replaced Standard exhaust with Delkevic end cans (with baffles in)
Removed and blanked off the PAIRS

So, too many changes to single out one culprit. But on a hunch, I'd be pointing at those main jets being too big, or the old boots leaking.

While I had the carbs off I fitted MCCTs. Can I just say to anyone doing this please use the guide on the forum! Don't be tempted to follow a youtube video as I did. A story for another day.
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sirch345
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Re: Can I use Dynojet needles with standard main jets?

Post by sirch345 »

sisumi wrote: Wed May 03, 2023 3:58 pm So an update from me. The bike now runs perfectly well, in fact a transformation over the jerky on/off throttle I was having before. It's my first v-twin after a load of fours, and I wasn't sure what to really expect - but after watching a few on-bike Youtube vids, it was clear they weren't having the low speed issues I was having. It now picks up smoothly from low revs and just keeps pulling.

So in total, I've:
Re-jetted to 178/175/45 (2.5 turns and 2.75 turns on the fuel screws)
Kept the dynojet needles (on the same clip position)
Replaced float valves and o-rings throughout carbs
Filled the third hole in the slide with epoxy
Replaced the carb boots (these had the 'restrictor' plate, but I fitted anyway, not sure how much difference they make)
Fitted standard filter
Replaced Standard exhaust with Delkevic end cans (with baffles in)
Removed and blanked off the PAIRS

So, too many changes to single out one culprit. But on a hunch, I'd be pointing at those main jets being too big, or the old boots leaking.

While I had the carbs off I fitted MCCTs. Can I just say to anyone doing this please use the guide on the forum! Don't be tempted to follow a youtube video as I did. A story for another day.
Well done it getting the bike to run properly :clap: :clap:
Good to hear what you have done :thumbup: :thumbup:

Chris.
Harveyz
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Re: Can I use Dynojet needles with standard main jets?

Post by Harveyz »

The most interesting part is the inlet boots - I did some digging on different forums and found something interesting on Super Hawk forum about the very subject. -Quote " Superhawks stalling under heavy braking or low idling. The deal is that since the carb throats are pretty big, under certain conditions, there isn't enough velocity to pull enough mixture from the carbs into the engine, and the bike stalls out. Honda fixed this in '99 by putting 5mm restrictor rings in the intake manifolds " - applying a bit of science - CV carbs rely on the velocity of the air to draw fuel - if velocity of air is low it will lean the fuel/mix - therefore reducing the diameter of the intake will increase velocity (The Bernoulli Effect). The reason your low speed problem may have been resolved may be due to the new inlet rubbers having restrictors. Mine is a 2000 reg (but 99 model year) - I've had the carbs on/off in last 6 months but never checked - I'll be checking. This also may explain why bikes rev smoothly when no load on the engine (mine revs clean as a whistle on the stand ) - engine will effectively slow the speed of the pistons due to load.

Love the handling on my bike (well sorted by last owner - WP shock, forks mod, 954 brakes) but low down power delivery driving me mad. I can see now why Suzuki engineers went for fuel injection on TL1000 which was released around same time. Thought owning an old Z1000 was interesting but VTR are whole different level of fiddling
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8541Hawk
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Re: Can I use Dynojet needles with standard main jets?

Post by 8541Hawk »

Harveyz wrote: Thu May 04, 2023 12:00 pm The most interesting part is the inlet boots - I did some digging on different forums and found something interesting on Super Hawk forum about the very subject. -Quote " Superhawks stalling under heavy braking or low idling. The deal is that since the carb throats are pretty big, under certain conditions, there isn't enough velocity to pull enough mixture from the carbs into the engine, and the bike stalls out. Honda fixed this in '99 by putting 5mm restrictor rings in the intake manifolds " - applying a bit of science -
This is completely wrong.
First the "restrictions" are to limit power for counties that limited bikes to 100HP nothing else. I will say I do have issues with that other forum as I was banned for life after I disagreed with the mod that EBC doesn't make the best brake pads ever but that is another story.
Now back to the stalling under heavy braking. The true issue is on the first gen bikes the hole in the carb stay that the bowl vents run through are a touch too small.(and Honda fixed this on later bikes by enlarging the hole in the stay, not adding restrictor plates) This can cause the rear carb to puke fuel. With the stock stacks, it runs up the rear stack and dumps into the shorter front stack and kills the front cylinder. The fix, per Honda, is to re-route the vent lines. You can either pull the lines from the stay and point them down or just remove them completely, which I have done and the problem is gone.

Image
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tony.mon
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Re: Can I use Dynojet needles with standard main jets?

Post by tony.mon »

Hawk, your post refers to stalling under heavy braking, and has merit for that problem.
Engine stalls at tickover is something else entirely, and it may be that the throat restriction speeds up fuel/air mixture in the intake stroke, reducing the tendency for the fuel/air to ignite in the carb on occasion before the inlet valve fully closed from the previous stroke.
That results in a spent charge being pulled in, which then doesn't fire as it should, and it's that which causes the drop in revs which can result in a stall.

I'm not sure that placing a restriction in the throat is a good compromise, because although it may reduce (not completely cure) the tendency to stall at tickover - especially when the engine is cold - it also restricts fuelling at full throttle, losing power.
That's how some bikes are made A2 or learner compliant, and don't develop as much power as they could.

Personally, I'd just increase tickover to 1350 or so, learn to ignore the odd carb cough and ride it, because increasing the tickover lessens the chance of the engine stalling.

Of course, fitting a lightened flywheel increases the chance of it stalling, but I'll happily accept that compromise to get a quicker-revving engine.

Oddly, when I fitted an ignition advancer, the problem disappeared- it might be that the fraction of a second earlier ignition prevented ignition of the incoming mixture, but the increments of time are so short I doubt that could be the case. Additionally, the intake stroke follows the exhaust stroke, so the inlet valves would have been closed for a significant part of the crank rotation before opening again for the inlet charge.

My best guess, for what it's worth?
Still-burning fuel/air flowing out of the exhaust valve as the inlet valve opens, igniting the incoming charge.
There is a part of crank rotation where both inlet and exhaust are both a little open.

That might be why, on SP1 and SP2 engines, part of the exhaust port is built up, speeding out the exhaust gas faster than on a Storm. In theory there should be better scavenge across the piston head if the exhaust gas flows out quicker.
They don't have the same problem of stalling at tickover.

Discuss...
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8541Hawk
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Re: Can I use Dynojet needles with standard main jets?

Post by 8541Hawk »

" Superhawks stalling under heavy braking or low idling" This line from the post is what caused my reply
Loud pipes don't save lives, knowing how to ride your bike will save your life.
Harveyz
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Re: Can I use Dynojet needles with standard main jets?

Post by Harveyz »

The aim of the post was to look at reason for the poor performance for VTR1000 in their lower rpm's off idle - which mine is suffering from. Sisumi - email made a point that he'd changed the inlet boots to later model restricted version and used 45 pilot jet - which was something which seemed worth exploring given airflow dynamic theory would seem to agree - faster airflow - richer fuel mix - universal fix appears to be 48 pilot jets.

For the record in Europe only the French and Germans were restricted bike to 100BHP and strangely the French bikes from 97 -03 were fitted with the unrestricted inlets "1622MBB950" like the UK bikes suggesting it was not to restrict bhp - in Europe only the German bikes were fitted with the restricted inlets "16220MBB610" for all model years of VTR. However from 2003 both UK and French bikes were fitted with the restricted inlets.

As Germany had stricter emission laws at the time - it may the reason for the original restricted inlets from 1997 - interestingly Euro 3 emission became law in 2003 in EU - All European VTR's moved to restricted inlet rubbers in 2003. The reason for the change may be to meet Euro 3 - the 2003 VTR1000 is listed as meeting the London ULEZ emission standards


https://www.bike-parts-honda.com/honda- ... 6220MBB950
https://www.bike-parts-honda.com/honda- ... 6220MBB610
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8541Hawk
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Re: Can I use Dynojet needles with standard main jets?

Post by 8541Hawk »

Harveyz wrote: Fri May 05, 2023 12:58 am The aim of the post was to look at reason for the poor performance for VTR1000 in their lower rpm's off idle - which mine is suffering from.
Well the first thing I would say is have you ever ridden a stock VTR? I ask this because the stock bikes didn't have a low RPM\off idle issue. The issues appeared when folks decided to rejet their bikes. As for the carb isolators, in the US we never had any restrictions in the isolators, in fact mine are actually opened up to match the carb throat and intake port and no issues. IMHO it leads back to the old saying " the bigger the CV carb, the harder it is to tune" So Honda had to do a good job with the stock settings in the first place. The issues seem to show up when folks decide the bike needs bigger mains or other jetting changes without really understanding CV carbs. This leads to the systems (pilots,mains, needles) being out of sync with each other which leads to running issues. The dyno might be your best bet to get things sorted.
Loud pipes don't save lives, knowing how to ride your bike will save your life.
tony.mon
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Re: Can I use Dynojet needles with standard main jets?

Post by tony.mon »

You're right, Hawk, these carbs don't always behave as you'd expect- for example, with gasflowed heads, high compression carbs, airbox and exhaust tuning, they need smaller mains rather than the larger ones one would expect.
Dyno is the way to go- or make and install wideband Lambda sensors and a display so you can see what is happening at any time.
It's not falling off, it's an upgrade opportunity.
sisumi
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Re: Can I use Dynojet needles with standard main jets?

Post by sisumi »

One thing that's not clear to me, if the restrictor plate is only to reduce airflow - and therefore power, why are they an uneven shape? Why not just make the overall diameter smaller? Seems (with my very limited knowledge of airflow), that there's something more than just a power restriction at play.

I did install them with the thought they may reduce power (72kw was marked on them). At the time, I just wanted the bike to behave itself. Whether the boots had any affect on that whatsoever, I really have no idea. Bear in mind, I'm no speed demon, so if I've lost a few bhp off the top end, I'd probably not feel it. One day in the future, I may well delve back into the carbs and have a play - but for now I'm more than happy with my 'Storm' :D

Si
Harveyz
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Re: Can I use Dynojet needles with standard main jets?

Post by Harveyz »

The saga continues. - thanks 8351hawk - trawled your posting and went back to basics - checked everything again - Delkovic Cans (road legal so close to originals ) , left main jets at 178Fr 180R (I haven't got a 175) , pilot 48, ops set to 494K, fuel screws Fr 2. R 2 1/4. |fired her up everything fine. - decided to go out to test - pulled cleanly from tick over - finally rideable.


here's the interesting part - I only had around 4l fuel int he tank - running low - bike ran fine - even stopped at a train crossing - got good and hot didn't stall. \stopped at the gas station - put 10l in (I've a 19l tank conversion). Then the fun started - hard to start - surging 2000rpm almost like fuel starvation - I thought back to the drawing board - road another 20 miserable miles.

Got back. - did some thinking - the last three test run I'd filled up with gas (different gas stations) - I'm think that now I have a tank breather problem
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