ESE's works engine tuner

**Bert** · 15th November 2015, 07:25

Originally Posted by chrisc

Question for Wobbly/Frits/anyone else with lots of inlet testing experience below

The Honda RS125 manifold changes went:
pre 95 NF4 (far right in photo) - Medium length rubber mount with a horizontal angle, small square 'stuffers'
95 to 97 NX4 (far left in photo) - Short straight rubber mount, longer larger stuffers
98 onwards NX4 (middle in photo) - Longer straight rubber mount, same longer larger stuffer and 95-97 NX4

Am I right in saying that the 98 onwards longer manifold was to increase lower RPM power? Would the short straight manifold be better for a highly tuned 125 for use on tracks with larger straights?

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Originally Posted by wobbly

The shorter old model straight rubber is best.
Here is a very old dyno test I did on a TM125MX motor we used to race in 125 National class karts, this was used with a VeeForce 2 and a bored SPJ powerjet carb..
Its a crap printout - used to be orange and red, but the short manifold looses no mid power, but is near 2 Hp up around peak.
The short rubber is obsolete and all but impossible to find.

Originally Posted by Frits Overmars

The NF4 was really a motocross engine; the slant manifold served to move the carburettor out of the way of the central rear shock absorber. The effect was twofold:
The flow was reluctant to follow the bend; it concentrated on the outside, so the reeds on that side were overloaded and perished, while the reeds on the opposite side could have been much thinner because they hardly saw any flow at all.
The same was true for the crankshaft main bearings: the left-side bearing hardly received any premix lubrication. And boy, were those Honda main bearings expensive.
The short straight manifold worked a lot better, as Wobbly wrote.
So why substitute it with the long straight manifold? My guess is: to better isolate the carburettor from engine vibrations.

Something for consideration.

98-2000ish didn't HRC released the redesigned Carb for the RS, shorter overall length and 'closer to slide' manifold mount and shorter bell mouth / intake track.
Not having the bits at hand to measure - I wander if the over lengths are the same? (Reed tip to bell mouth).

The float bowl extends in front of the manifold mount and behind bell mouth - Must find photos (husa help me out)...

Older model

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Later model

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Please don't ban me from the thread...

**speedpro** · 15th November 2015, 07:27

Maybe there is a way to block people from posting to the thread? Or we could all just block the individuals

**husaberg** · 15th November 2015, 08:35

Originally Posted by Bert

Something for consideration.

98-2000ish didn't HRC released the redesigned Carb for the RS, shorter overall length and 'closer to slide' manifold mount and shorter bell mouth / intake track.
Not having the bits at hand to measure - I wander if the over lengths are the same? (Reed tip to bell mouth).

The float bowl extends in front of the manifold mount and behind bell mouth - Must find photos (husa help me out)...

Older model

Later model

Please don't ban me from the thread...

The Keihin shorty used on some KTMs and Kawasaki KX and likely other is about 15mm shorter than the traditional Keihin PJ
They also come with the Solenoid PJ and TPS.
The SPS sure seems even shorter in the bellmouth area.
Wobbly had mentioned the shorty Keihin years ago along with how to modify the PJ to raise its exit to higher up.

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I have one here I brought from Rob

**lodgernz** · 15th November 2015, 08:57

Originally Posted by F5 Dave

Yeah cmon guys. Most of the issue are 4 stroke riders posting late at night. If you want to get drunk and stick it round a bit, and I've been guilty of internet cajoling after a few bevies, - But please leave this thread alone. It is a unique and long running resource.

Yes, sadly, many New zealand men who are nice people when sober, just can't go a night without drinking, usually by themselves, then doing stupid shit. Of course none of them admit to being alcoholics.
Let me just say to the trouble-makers: This thread has a wide following around NZ and, since we all know who you are, you can be sure that destruction of this thread as a result of your negative posts will have repercussions in your lives.
Frankly, if you don't race or tune 2-strokes, you have no reason to be reading this thread, let alone posting on it.

**WilDun** · 15th November 2015, 09:35

Originally Posted by speedpro

Maybe there is a way to block people from posting to the thread? Or we could all just block the individuals

No doubt I will be criticized for this! but ............we have quite a few "real world" experts here who actually know about two strokes - and even four strokes! and who are very happy to contribute their knowledge, all of which has been earned by single mindedness, enthusiasm and hard work.
Amongst these experts there will always be differences simply because there are often different ways of achieving similar results.
Most of these guys are wise enough and strong enough to moderate their views, listen to someone else's point of view and comment on it in an orderly manner.
Unfortunately however, some will react indignantly and start swearing! (and I can swear with the best of them) - that is just a fact of life and can be tolerated to some extent when the discussion is going to eventually come to (at least) some sort of an agreement.

In everyday life, this reaction stands a (slightly) better chance of working, due to being able to interperet the gravity of situation by facial expressions. ( ie. If you see a face in a 'knot' you know to steer clear).
This happy situation however does not exist in forums, where the written word reigns supreme and I feel that swearing has really no place in the written word (except the odd little exception here and there when necessary).

It is also often used where some guys have run out of something meaningful to say, or whose limited vocabulary stops them from getting their message across in the written word.
Then there are those who swear just because they don't really know any other way, are pissed off (or maybe just pissed!) and then those who just who want to appear as mean guys (ie "bad ass" to our American friends).

The main point is that - these guys who are contributing their hard earned knowledge on this forum do not have to do that, they do it because they get a lot of pleasure from it and if they go, this great thread will just sink into the shit (sorry sewage) like so many threads on other forums have done!

This forum is very privileged to have them on it at all!

Yes I know I sound like a born again preacher and I know that I don't have a helluva lot of knowledge on this two stroke subject, don't ride bikes anymore and don't contribute much (like many others) - but I like it and as I don't have anybody at home to share this stuff with, this forum is the escape - it probably is for many others as well.

To see it get to this stage is pretty sad - TZ is just trying to carry on (as he always has done), but some of these people are so shortsighted they can't see what they are doing to his thread.
The moderator is repeatedly asking them to keep their petty opinions to themselves (in a gentlemanly way), but they obviously don't read his messages or see the mood of the contributors in general, or maybe they're just plain ignorant, can't see ahead and are only concerned with their own petty squabbles.

This thread is not for arguments, yes maybe some sensible debate - but there are plenty of other forums on the net where the subject doesn't really seem to be of any importance - BUT NOT THIS ONE!

Sorry for the "sermon"

**WilDun** · 15th November 2015, 09:46

Originally Posted by lodgernz

This thread has a wide following around NZ .....
Frankly, if you don't race or tune 2-strokes, you have no reason to be reading this thread, let alone posting on it.

I might add, this thread has a wide following around the world!

Sir, would you like to retract your last statement ? - that would exclude me completely and we just can't have that!

**sidecar bob** · 15th November 2015, 09:54

Originally Posted by lodgernz

Let me just say to the trouble-makers: This thread has a wide following around NZ and, since we all know who you are, you can be sure that destruction of this thread as a result of your negative posts will have repercussions in your lives.

I'm trying to stay away from this thread out of respect, but I have to say, that is an extremely disturbing statement to make.
Could you please describe what these "repercussions" may be?
I trust you heard about Paris yesterday?
Here's an idea to get this thread back on track, everybody accept everybody else's contribution & opinions for what they are for the betterment of the topic, as refusal to even consider another's point of view doesn't come across as knowledgable, it comes across as arrogant.
Maybe watch this clip to the end, it illustrates what I'm saying, change the topic to two strokes.
https://m.youtube.com/watch?v=55h1FO8V_3w

**F5 Dave** · 15th November 2015, 09:57

Ok we're all friends again now. Let's get back to the 2 stroke talk.

Erm. . Well I'm working on my 1970 T125 Stinger at present. It is a nut and bolt resto road bike so I'm not going to tune it even slightly. It'll be a first.

Ports are iron so the philosophy will save bulk time.

Although it might help the cooling if I got the squish actually close. But I'd have to scoop the heads a little. . .

**Sketchy_Racer** · 15th November 2015, 10:06

Well in an attempt to get this thread back on track to two strokes, I've got a couple of questions that I am curious about with the NSR300s that we run.

Is running Ram air box a benefit to these bikes on NZ tracks? The reason I ask is there must be a point at which below that certain speed the ram air would have zero effect but at what speed does this become an advantage?

Also what effect does the ram air have on jetting. Is it required to run richer jetting to compensate for the ram air effect of do the carburettors sort themselves out.

For me it seems like a lot of extra complexity for potentially minimal gains, but I have no experience to know if it might be more than a minimal gain!

Anyway here is nice photo of the chambers that I'll hopefully be running for the Suzuki Series this year. We've had no end of problems with the stainless steel ones cracking so with a bit of luck the mild steel ones will be the good. I still plan on continuing with the hydroforming but between Work, Exams, Wedding and race season coming up there are just not enough hours in the day!

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Cheers,

Sketchy

**Sketchy_Racer** · 15th November 2015, 10:07

Originally Posted by F5 Dave

Although it might help the cooling if I got the squish actually close. But I'd have to scoop the heads a little. . .

That's a slippery slope you're on to tuning there Dave!!

**136kg136ps** · 15th November 2015, 10:15

Frits,Wob and others who post interesting and informative info.Please advise the rest of us where you may be found in the case your efforts are not given due appreciation as there are far more lurkers and those inspired by your efforts than you realise as well as a great deal of implications to our respective sports.

TZ started this as a simple build thread but as time has gone on the additions from Husa,Wil,Ken,Smitty and many others has turned this into the most informative,in depth,historical and practical compendium of 2 stroke knowledge available openly anywhere.Bravo to all on all that has happened so far.

**husaberg** · 15th November 2015, 10:27

Originally Posted by Sketchy_Racer

Well in an attempt to get this thread back on track to two strokes, I've got a couple of questions that I am curious about with the NSR300s that we run.

Is running Ram air box a benefit to these bikes on NZ tracks? The reason I ask is there must be a point at which below that certain speed the ram air would have zero effect but at what speed does this become an advantage?

Also what effect does the ram air have on jetting. Is it required to run richer jetting to compensate for the ram air effect of do the carburettors sort themselves out.

For me it seems like a lot of extra complexity for potentially minimal gains, but I have no experience to know if it might be more than a minimal gain!

Cheers,

Sketchy

**teriks** · 15th November 2015, 10:48

Originally Posted by Sketchy_Racer

Anyway here is nice photo of the chambers that I'll hopefully be running for the Suzuki Series this year. We've had no end of problems with the stainless steel ones cracking so with a bit of luck the mild steel ones will be the good. I still plan on continuing with the hydroforming but between Work, Exams, Wedding and race season coming up there are just not enough hours in the day!

Cheers,

Sketchy

Wow, someone knows how to weld!

**teriks** · 15th November 2015, 11:00

Originally Posted by Frits Overmars

Neil, if I'm not mistaken you're playing with the Profi F2A engine that happened to cross my desk when Profi started producing our MB40 F3D engine.
I dug up some old files: 190° exhaust timing, 140° transfer timing and 0,14 cc combustion volume, does that sound about right?
I found a huge mismatch between blowdown angle.area (good for 26500 rpm) and transfer angle.area (good for 44000 rpm) but as Profi was happy with its performance, he decided not to change it, so all I did was calculate some pipes. If I remember correctly pipe #1 would be delivered with the engine while pipe #2 was experimental.
All pipe lengths are from the piston edge; all diameters are internal. Notice the narrow header and the 4,2 mm stinger diameter on #2?
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I have seen plenty of such a mismatch in (great performing) F3D engines, including MB's, although not as extreme as the Profi F2A you described.
Have no clue why you'd want that, other than a very loose theory that it could have a positive influence on ignition timing and perhaps combustion.

**WilDun** · 15th November 2015, 11:47

Originally Posted by sidecar bob

Here's an idea to get this thread back on track, everybody accept everybody else's contribution & opinions for what they are for the betterment of the topic, as refusal to even consider another's point of view doesn't come across as knowledgable, it comes across as arrogant.

Ha Ha, good clip! - and I can see that you have now become a "reformed" character - good boy, have some cake!