Re: Hero Impulse ownership experience

I've got those braces. To be honest, if you have access to milling equipment and half a brain you could manufacture a much sturdier version. I've got the idea, but no equipment.

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Re: Hero Impulse ownership experience

[QUOTE=Krishna Gopal Das;1102232]I've got those braces. To be honest, if you have access to milling equipment and half a brain you could manufacture a much sturdier version. I've got the idea, but no equipment.

Can you share the idea and some pictures of the braces?? Both mounted and before mounting. I have access to an Industrial unit

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Re: Hero Impulse ownership experience

Saw your Facebook page - lovely ride photos and an enticing destination...

If your bike is missing even at 6,000ft, you probably DO need a new filter - BUT I had the same problems with misfiring on my brand new bike (and brand-new air filter) here just above Manali at 7,500ft or less. Sparkplug was showing absolutely black / sooty. There is no problem with the airbox / intake tract itself, so far as I can tell. I'd referenced my TeamBhp thread and my foam air filter element mod earlier here: Replacing the KB-RTZ offroad specials - My Hero Impulse - Team-BHP (see post #48), which I'd recommend checking out.

Just doing that foam-element conversion COMPLETELY changed my tuning (made it MUCH leaner), which demonstrates just how restrictive the stock filter is. With the paper element, I'd initially been forced to go down to a #118 main jet (down from stock #132) for Manali and beyond, which at least made it run well enough at full throttle over the high passes (up to 17,600ft). Now with the foam element, am back to the stock 132 and it runs decently at 13,500ft (won't say quite perfectly, but nothing to spoil my fun), with good plug color.

Other BIG key to proper tuning is to lower the main needle. Unfortunately, there are no grooves / c-clip in this needle like on many other carbs, so technically unadjustable. Best workaround is to remove (by filing or otherwise machining) about 1mm from the bottom of the needle flange - this will lower the needle the equivalent of one notch. When you're back at lower altitudes, just put a 1mm thick washer in there to raise it back up to original height again and prevent over-lean (and over-hot) operation. This, too, is outlined on the TeamBhp thread (post #22).

Anyway, I feel your pain. My ride out to Ladakh this past June was pretty stressful on account of how badly the engine was running - and that was with the 118 jet! On the way back around Pang, I finally couldn't take it anymore and on the roadside opened the top of the carb / modified the needle (used a diamond flat file from my kit) to lower it - and the rest of the ride was much, much more pleasant.

I think that with the foam element and a 1mm drop of the needle alone, you'd be having plenty of carefree fun between 6,000-12,000ft (I surely do!). If you want to retain the paper element, you'll have to go with a smaller main jet for sure. Everybody has trouble with these bikes (when stock) at altitude. Many have claimed that removing the air filter for the Manali-Leh ride did the trick - but who wants to run unfiltered on those dusty stretches??? And besides, it actually requires less work (total 12-13 screws) to change a jet AND lower a needle (once the mod is done) than to remove the side covers, seat, airbox cover, and air filter (16 screws). And you're not going to ruin your engine.

Re: the steering cones, main thing is not wear (I think), but that they keep coming loose / not holding adjustment, sometimes requiring attention (in rough road use) in as little as 50km, in my experience (tightened these a dozen or more times in 3,000km). I need to get into it a little more next time, but think the locknut on top was not actually locking in the adjustment, i.e., not actually driving the top plate of the triple clamps down against the upper adjuster nut/cone as it should, for some reason. This last time after adjusting the cones to zero-play, I gave the top plate a little extra downward persuasion with a hammer before tightening the top nut, and so far after several hundred km's, it's holding. Wondering if the hole in the top plate is too tight a fit on the steering pivot shaft? Will look into that a bit more next time it loosens, and post here (or Tbhp) later.

-Eric

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Was a pleasure meeting you (and that hardcore senior companion from Calcutta) the week before the rally at the Koksar checkpost (Rohtang backside). Later saw him tearing back through Bahang (just north of Manali) a couple days before I thought the rally was ending, so not sure if he completed all the stages or what??? And never did see you after that -how did you fare yourself?

BTW, my phone went bad and lost access to both your phone #'s. Please re-supply me by PM, if you don't mind. Realize you must've been rushed, but do feel free to stop in to see us next time you're around Manali.

-Eric

Re: Hero Impulse ownership experience

[MENTION=72938]ringoism[/MENTION]
Thanks a ton and very right and spot on. Day before after i reached home I took some time out an.d opened my carb. Yepp 132 the mainjet was. On enquiring about the sizes of the same on other 200cc+ bikes out there...turns out none has a jet this bigger. Still..but 132for a mere 150cc mill is darn big..ad with that paper type filter the A/F ratio becomes rich quickly...and these two factors add up to why it behaves that way at not so high altitudes like 7000+ft which it shouldnt.
So every measure one's gotto take it either to get the fuel low or the air high. And yepp the low 118jet could do...or the more free flowing air filter.

I thought of pulling out the air filter back in the ride at that altitude but it was climbing fine not that good though but kept calm and moved on.

Btw that needle drop in the groove is a technique i used to practice on my Yamaha Rx...helps a great deal. Funny yaah..theres none on this carb though. Still your way of filing and putting a washer later is a nice jugaad. Will surely try that out, post trying the air filter mod. Wont go changing the mainjet to lower sizes now.

And that Tbhp thread...well thats a big thread and feels very informative too. Will check that out in a stretch ! And great help guiding Impulsers here. Thanks a ton.

Re: Hero Impulse ownership experience

Hello guys...

I am hearing a squeaky sound from my rear suspension. I had mentioned it to ASC but as usual they did not rectify it. This time it was my first paid service and they only changed oil and that's all. :banghead:

Now this sound is increasing and I feel suspension is getting hard. Any suggestions.......

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Re: Hero Impulse ownership experience

Stripped off the paper element from the casing and attached a layer of foam (used a new Pulsar's filter).
Its breathing more easily and bike is more relaxed now.

Re: Hero Impulse ownership experience

I was a little perplexed about the extra large main jet size even vs. much larger engined bikes - till I came across post with a little carb sizing theory on a U.S. drag racing tech forum.

Thing is that the Impulse has a kind of oversized carburetor to begin with - 28mm bore, vs. the Unicorn at 25mm and the 150DTSi (which has higher bhp) @26mm. Not sure what Hero's reasoning here was, because 28mm is a lot bigger than necessary to support 13+bhp - but anyway: With a larger carb and a relatively small displacement engine, air velocity is less through the carb bore, and less vacuum is created in the venturi; and since it is vacuum that pulls fuel up from the bowl into the airstream, then a larger jet is needed to get the same amount of fuel into the engine as one would with a smaller-bore carb. So the bigger jet is surprisingly not necessarily going to make it run richer. A big jet with low vacuum will flow the same as a relatively smaller jet with relatively more vacuum. Make sense? So if you had that same 28mm carb on a 200+cc bike, there'd be more vacuum created (more flow due to a bigger displacement piston sucking air through the carb), so it can actually run a SMALLER jet and still have the same air/fuel ratio. Weird, eh? Seems counterintuitive at first! So the Impulse probably has the largest main jet of just about any Indian bike, because it probably has the most oversized carb of any of them, taking displacement into consideration. Old iron Bullets, having rather undersized carbs (26mm maybe) actually had #95 main jets! Lots of vacuum = plenty of fuel flow through even a small jet.

That said, I'm wondering whether Hero might've set the bike up just a little richer than normally very lean-tuned Indian bikes tend to be, simply because unlike most other bikes, it has a catalytic converter - and cat's can't be run too lean. If they are, they 1. become ineffective; 2. can seriously overheat (the Hero tech up here was asking if I had any ideas as to why his friend's Impulse exhaust (in the cat area) got hot enough to melt the airbox mounted a couple inches above it...

-Eric

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Nice work. Only thing to keep in mind here (as I also have to with my setup) is that the actual surface area of the filter is much less than the paper one, since the paper one is all folded up accordion-style. So you and I MIGHT have to check/service them more often. Good news is that the foam can be quickly washed, re-oiled, and reinstalled, instead of having to pay for a new paper unit each time. My foam was installed just like yours at first, later I removed the whole thing and picked up a little extra (maybe 30-40% ?)surface area by sandwiching a larger piece of foam between the airbox and cover itself.

Re: Hero Impulse ownership experience

^^well that carb size and vaccum built up accordingly was an insider. Great stuff, helped aa lot.
And the foam filter(for the while is this way) needs to be redone in a more refined way. Saw CBZ's foam filter too, large surface area its got, pretty thick and large w.r.t this pulsar ones. Anyways didnt got time lately to take it to higher altitudes. Will do the same in a couple of days.

Re: Hero Impulse ownership experience

Can anybody suggest me... Using a MRF tube size 100/90 in impulse rear ceat tyre size 110/90 is a good idea or is it important that size should be same?



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Re: Hero Impulse ownership experience

@ringoism

First of all I want to thank you. People like you add real value to forums such as these. I have read your complete thread on impulse ownership on tbhp and I don't even own an impulse..!! And right now I am literally coming from reading up your complete thread on the Marshall ownership and your posts have been so entertaining, endearing and informative that I just wanted to thank you for all the content you have added to these forums. I myself am a lurker on xbhp and the buggers at tbhp never let me join (I mean for gods sake how many right answers can there be to the question - which is GTO's fav car???!!!???) so I could never thank you directly there and so here. Over all I see that you have led (and are leading) an extremely interesting life and I for once will be an audience for as much as the internet forums allow me to..!!

I personally am a total 4x4 nerd apart from loving motorcycling and being an in general petrol head. The one vehicle I own - a humble Honda Dazzler - is a bit modded, with a 170 cc bigbore, higher compression piston and some head porting work. Apart from a carb which has been tuned by solely by me.

So I wanted to share what I had read about impulse carb when I was doing my own research in the quest to get my af mix perfect.

Impulse is a derivative of a proper dirt bike. And dirt bikes live most of their lives in the mid to "higher-mid" rpm range. In the typical dirt bike application the engine is always on a boil however the vehicles speed itself is never very high. Therefore the older tech air cooled engines on such bikes were prone to over heating. Because the low vehicle speed was unable to flow enough air through the engine fins to cool it down.

Therefore the engine cooling was done not by air - but petrol..!! And hence the large main jet size of "most" dirt bike carbs with air cooled engines. Because of the larger main jet more petrol can enter the engine and cool it. The petrol cools the engine by absorbing the engine heat to change its state from liquid to vapor.

So this is the reason for larger main jet size in impulse. And yeah even as far as I know the impulse main jet of 132 is the largest amongst bikes in India.

This kind of is the reason why impulse becomes "particularly" unsuited for high altitude application, because in the mid range the engine is literally flooded so badly by petrol that there can hardly be any decent combustion. Also the reason why when you did the paper to sponge air filter mod things improved pretty drastically.

Now my thoughts regarding a bit about carb bore, engine vacuum and amount of petrol that can sucked in from the main jet, referring to what you say in the post above.

Again - all this is just from what I have read, what I understand and the experiments I have done on my own bike.

It is true that a smaller carburetor bore will mean higher air flow velocities and thus more petrol sucked into the engine. But this happens only in theory and not in practicality. This is because here we are looking at three variables here engine size (cc - and thus the vacuum it can create), the carburetor bore (26mm? 28mm?) and main jet size. For some very good reasons (which I will elaborate more on later) the variable which limits fuel intake into the engine is not cc (vacuum) and not carb bore but the size of the main jet..!!

To corroborate this claim I will give you my personal experience - when I got my engine changed to the big bore - a bump of 20cc (from 150 to 170) I had also assumed that higher velocities in the carb and more vacuum in the engine cylinder will manage to suck in more petrol from carb - but that did not happen - the engine was running pretty lean. Limitting factor was the main jet.

Now that I have upsized main jet from 115 (stock) to 125 (stock karizma) the A/F ratio is completely in its sweet spot. However fact remains that the engine can get even more petrol if I change the main jet to 132 (impulse). But it is not enough to feed the engine more petrol to get more horses. The petrol fed should also be uniformly atomised so that the engine can burn it cleanly. The jets of carb serve the dual function of metering the amount of fuel going in - as well as atomizing that fuel.

Larger main jets are not able to atomize the fuel as efficiently as smaller main jet - again pretty basic fluid dynamics. However that is a good thing for bikes like impulse - which are meant to be dirt bikes - where the fuel vaporization is done by the cylinder heat leading to engine cooling.

So in summary - whereas high flow rates (24mm carb) + small main jet (115) and low flow rate (28mm carb) + large main jet (125) should theoretically end up giving same A/F ratio - in practicality this does not happen because limiting factor in metering fuel is not flow rate but main jet size.

So there - I am a long poster just like you!! :P And all this is from what I have read on the internet. I have zero formal education in engineering or what ever - but I tinker around. Would love to get your response on all that I wrote. And yeah - once again - thanks..!! Your writings have entertained many an evenings of mine..!! Keep at it!!

Re: Hero Impulse ownership experience


Thank you for sharing this wonderful wisdom with all of us. I can't speak for the entire bike community, but I am definitely thankful to you for sharing. I will consider all these points when I get around to upgrading my steed for performance.

Keep sharing your wisdom!

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Re: Hero Impulse ownership experience

My Impulse woes have started at 12000kms.
My mech told me its time to change the air filter so i went for the K&N. The foolish shop from where i bought it installed it all wrong. IF YOU HAVE AN IMPULSE WITH A K&N PLEASE READ THIS..
Do not install the cone directly from the carb outside the air box. Thats how it was fitted on my bike for the first day. Sounds cool, people will check it out, you will feel awesome, girls will chase you.. blah blah blah.. TILL IT RAINS.. Unluckily (luckily actually) it rained the next day. Bike didn't start, choked it till the ASC. My ASC guy is the best! He is all for mods, all he wants is to do it himself (for free!). He installed the cone inside the old air box, removed the old element and a cap to make airflow easier. PERFECTION! This, the iridium spark plugs with the copper cables and the FS Oil had finally perfected this engine (for me)..
Now my electrical woes have started. It rained the whole week. The console is off, i saw water drops inside.. yes OFF.. no tacho, no speedo, no indicators. My HID(and stock bulb) is working fine, my horn (Bosch Air horns) are fine, brake light is fine, neutral indicator is good and even the self start is fine.
What do you guys suggest? I live 90kms from Chennai and visit the city only on weekends. SO don't really have the time for the mech to brainstorm on this. Please suggest!

Re: Hero Impulse ownership experience


hi
can you please upload some pics of your air filter how it is fitted

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Re: Hero Impulse ownership experience

contacted my asc and he said that they will replace the console for free! i bought the bike in august 2013, so this is cool! i will take the pictures then..
on a side note, he is trying to convince me to let him take off the catalytic converter and free flow up the exhaust. will this add to any power?i do highways 80% of the time and need it.. i have considered changing the sprocket but am avoiding it since that equates to a top speed vs acceleration kind of deal.



btw is it just me or is anyone else here waiting for the ktm adventure?

Re: Hero Impulse ownership experience

I'd buy any reasonably priced dual sport in a heartbeat, an factory Impulse 223cc included.