[creative420]

That was a beautiful write-up, Eric. Love how your bike has treated you. I was in the market for a used impulse about a year ago but canned the idea as I needed to direct my finances towards something else. Now, maybe, I can reconsider it all over again. Will call up a few Hero dealers in Bangalore and see what they can do.

[RenuKumar]

Dear Tbhpians,

I'm a proud owner of the Hero Impulse, great bike and my upgrade to 200cc makes it even better. Till 100, it is very efficient and it is giving me thorough happiness. However, I am not happy on long rides as the top speed performance is a concern and reliability is bad. I want to know if the bigger Impulse is in plan or should I just plonk in the ZMA engine. If the answer to my first question is no, please advice me on how to upgrade the engine. I am from Bangalore and I would like to know who does a good job and PLEASE help me understand the wiring, exhaust, carburetor etc. No other bike is giving me the happiness of Impulse. Please help!

[Asta_la_vista]

Hero may not release the bigger Impulse in the near future. Remember reading in the early editions of Overdrive about a mad Impulse. Can't exactly remember the edition month. You can have a look at the Youtube channel of Overdrive.

Regarding the garage, as you are from B'lore, you can try Indimotard. They are the best when it comes to motorbikes. AFAIK they are pretty enthusiastic guys.

Regards

Prasanth Krishnan

[IshaanIan]

I'm not sure if you can legally change the motor and have a valid RC and Insurance. Why not try riding the Himalayan? Should suit your requirements pretty well.

[ringoism]

Having been given the unexpected opportunity to be out in Lahaul/Spiti around the time of the Raid-de-Himalaya - which must provide one of the most beautiful racing venues in the world - I was happy to be able to witness some of the action at Batal. Good showing of Impulses out there, some plodding along rather painfully but a couple seeming quite well-ridden:




I'd ridden mine out there last year (not rallying), and can't say that it was really able to "flatten out" and fly along at speed over the huge gravel bits so effortlessly in the way my the old KB125 had (the lighter viscosity shocker oil I've since installed might help it there)... nor did it have quite the power available to urge it on.

At the same time, with the one saddening Raid fatality firmly and soberly in mind these past days, as a man similarly in his late 40's a sub-15bhp bike is seeming a little more plausible than one with four times that power. At Chachu's dhaba in Batal, two days before a certain big-bore KTM would send its rider flying to his demise, I sat with another man in our age category - a Triumph Tiger rider - who was withdrawing on account of an accident that could've been serious: "I was pressing it too hard" he said, "I'd kept ahead of the WR(450) for a long while". Despite the back/leg sprains and a torn-off fingernail and wrecked bike, he was fortunate to be walking away from it and I told him so.

Not saying here that age need be a limiter of dreams, ambition, victories or straight-up fun... just sayin' that for me personally, my slightly modded Impulse is feeling generally strong enough as of late (but I'm still going to get that 'pipe on there when I can get around to fabbing it). Set up / ridden right, they would seem reasonably capable machines.

-Eric

[ringoism]

Originally Posted by IshaanIan

I'm not sure if you can legally change the motor and have a valid RC and Insurance. Why not try riding the Himalayan? Should suit your requirements pretty well.

Well, the Himalayan is an entirely different machine from the Impulse and despite its breaking new ground, for lack of a better descriptor could still be considered very "Royal-Enfield-like" (heavy, bit cumbersome, lots of mechanical noise, etc), perhaps especially for one already experiencing "thorough happiness" on a Hero product.

I've had a couple different RTO's/ MVI's tell me that engine swaps could be endorsed - one inquiry was with respect to the MDI turbo swap for the Marshal, the other was with respect to this Impulzma thing. Other RTO/MVI's may contradict this, of course. Probably a question of interpretation of the applicable laws / the level of cooperative spirit discoverable in a particular office.

Originally Posted by RenuKumar

Dear Tbhpians, I'm a proud owner of the Hero Impulse, great bike and my upgrade to 200cc makes it even better. Till 100, it is very efficient and it is giving me thorough happiness.... top speed performance is a concern and reliability is bad

Can you give any details about your 200cc upgrade: who did it, how it's done, what's the cost??? You mentioned reliability issues - What problems specifically?

Thanks,
-Eric

[RenuKumar]

Originally Posted by ringoism

Can you give any details about your 200cc upgrade: who did it, how it's done, what's the cost??? You mentioned reliability issues - What problems specifically?

Thanks,
-Eric

Hi Eric, I have used the Karizma piston to upsize the bore and increased the valve sizes to accommodate more fuel inflow and exhaust gases. I have also used the carburetor of Pulsar200 and have put a K&N free flow air filter directly on the carburetor without doing the plumbing works. However, I have not used the free flow exhaust which is the main problem.

The main problem that I am facing is with the clutch plates which burns at about 1000 kms of run. The power delivery is excellent but my mechanic says that the clutch plates are not able to take the increase in power. He was saying that upgrading to fiber clutch plate will resolve the issue. I request you to help me with the clutch plates and exhaust please.

[ringoism]

Originally Posted by RenuKumar

Hi Eric, I have used the Karizma piston to upsize the bore... However, I have not used the free flow exhaust...The main problem that I am facing is with the clutch plates which burns at about 1000 kms of run. The power delivery is excellent but my mechanic says that the clutch plates are not able to take the increase in power. He was saying that upgrading to fiber clutch plate will resolve the issue. I request you to help me with the clutch plates and exhaust please.

AFAIK, the Karizma's bore is 65.5mm, and the 150's is 57.3mm. Did you have to re-sleeve the original cylinder to accommodate the 8mm increase, or was this a direct overbore? Also the 150 has a dished piston crown, whereas I think the Karizma's is a flat-top - if I calculate correctly, that would with the overbore would raise compression ratio from stock 9:1 to 12:1, which is generally going to call for especially high-octane petrol. I could probably get away with that CR up here at 7,000+ft (rarified air), but nearer sea-level, have you had any detonation ("pinking") issues? I'd thought to shim up the cylinder block a couple mm's to help correct this. Also wondering if you noticed any more vibration at any rpm, as the Karizma piston is much heavier than the featherweight 150's. Lastly, I'm guessing you had bushings fabricated to adapt the original piston's small wrist-pin to the larger pin bores in the Karizma unit? Was that your bike's mods I saw detailed on xbhp?

Re: the clutch I'm a little surprised you're having that much trouble, unless you're in the habit of "half-clutching" (which should definitely be avoided in normal riding). Don't know what options are there for disc materials, but along with (or instead of) that I'd think about simply installing stiffer clutch springs - effort on the handle will be higher, but if you can handle that, it'll definitely reduce slippage/heat/wear/failure. You could bring a stock spring with you to whichever industrial supplier and ask for something with a slightly larger wire diameter. I can't remember whether the Impulse has four or six springs, but anyway I'd expect this to be a big help.

Re: the pipe, the stock one has a very small ID in that primary bend, and must be very restrictive; the stock silencer also creates a lot of backpressure (you can feel/hear it being forced out the condensation drain hole), and I'd expect substantial performance gains with a free-flowing upgrade. Eventually I'll probably fabricate at least the silencer ("can") portion myself, straight-thru with perforations and stainless wire mesh and maybe some ceramic fiber packing inside for noise-control. I suppose some off-the-shelf item should also be easily enough adaptable. The front portion of the pipe is the harder part; might try making one of those too, but the bending will not be easy without a mandrel type setup, especially if I'm doing it with stainless. There are some juggad type tricks for this that may or may not work. None of this is probably going to happen before next Spring, but I'll let you know if/when I get something worked out.

Thanks for your info/inputs and happy motoring,

-Eric

[Sutripta]

Originally Posted by ringoism

Re: the clutch I'm a little surprised you're having that much trouble, unless you're in the habit of "half-clutching" (which should definitely be avoided in normal riding). Don't know what options are there for disc materials, but along with (or instead of) that I'd think about simply installing stiffer clutch springs - effort on the handle will be higher, but if you can handle that, it'll definitely reduce slippage/heat/wear/failure. You could bring a stock spring with you to whichever industrial supplier and ask for something with a slightly larger wire diameter. I can't remember whether the Impulse has four or six springs, but anyway I'd expect this to be a big help.

Locally made springs is something I've learned to be very wary of.

Regards
Sutripta

[ringoism]

Originally Posted by Sutripta

Locally made springs is something I've learned to be very wary of.

Regards
Sutripta

Probably with good reason - but I wasn't suggesting "locally made" in the sense of low-grade desi. Some industrial suppliers in India have good quality stuff available, whether imported or those of well-produced domestic manufacture. Every new car/bike in the land is full of domestically-produced springs of widely varying types / sizes.

In the case of a motorcycle clutch, worst-case scenario if something low-grade was fitted would seem to be a spring breaking... which wouldn't cause any kind of catastrophic failure / damage the way a bike clutch is configured. It'd probably just start slipping.

-Eric

[trnaren]

Folks chance upon this thread when i was browsing to find options to mod my Impulse for a ride from Delhi to Leh in June. Very detailed, interesting and passionate views.

Till date I have attempted simple mods like wider renthal bar, better grips, bar raisers, motocross foot pegs, higher seat height, etc to improve ergonomics. Also replaced the stock spark plug with iridium ones and threw away the top cover to the snorkel in air box. Have dabbled with motul syntetic oil, etc.

My impulse experienced serious breathing issues when i did a trip delhi-kufri-sangla-kaza-rackong pe- shimla- delhi about 4 years back.. managed at that time by punching holes in the stock filter.

however, now i have taken the plunge and am upgrading to a karizma engine @indimotard greasehouse in bangalore for the ensuing trip. Will also change the carb, air filter and exhaust in this process. Anxious and excited about the new avatar which will be ready sometime next week.

though it will burn a hole in my pocket, am hoping have a good time on the ride.

Any suggestions are welcome!

[utpal]

All the best for the modifications and the upcoming trip.
Any details you are willing to share - cost of the mods, how the bike feels after etc would be most welcome.
I still see Impulse as a bike I would love to pick up (especially after reading about so many bad experiences of 'Himalayan' owners)

regards,
Utpal

[ringoism]

The latest addition...





Picked these up over the winter in Mizoram... where there are a LOT of excellent bike accessories shops...

Bolted right on with no adjustments / interference issues.

The handguards have plastic spines vs. the aluminum-framed Acerbis of otherwise identical design I found online from suppliers abroad (which cost many thousands)...

But the quality is nice, and if they're fakes, they seem to be good ones. Rs1,300 seems a reasonable price to pay for warmer / drier hands, some protection from brush (yes, useful for entering my parking daily) and some added visibility.

I'd kind of been searching for red ones to match the bike, but as it turns out, these match my new hi-viz AFX helmet perfectly... I get a lot of compliments on both, and they actually seem to complement the red bodywork.





The retina-burning colors certainly can't hurt safety-wise; there is no doubt that people can see me coming down the road now.


Since 2017-onward bikes are full-time headlight on, we have a lot of additional help with two-wheeler visibility (and happily I can ride with mine on all the time, as I have for years, in the confidence that before long I won't have every third person along the road signaling me that my light is on... (yes, I know, thank you very much, I am just some idiot who's a bit ahead of my time).

So speaking of that, I've swapped in a 55/65W OSRAM halogen recently (that I'd taken out of the Marshal at some point and which shares an identical mount), which really is a HUGE improvement at night - about the best bang-for-the-buck I've spent on this bike. Flash-to-pass still functions as it should, so stator is apparently of sufficient capacity for both filaments to be lit simultaneously. And so far no melting of my reflector. I also have a 40W LED unit brought from abroad that I'll probably install when I have time, which should be simply brilliant.

-Eric

[ringoism]

First off, I've got two red bikes now:

re: the KB-RTZ thread, in case I haven't mentioned it earlier:

http://www.team-bhp.com/forum/motorb...kyard-dog.html


Secondly, a little Impulse tech:



(Right to left: The original 28mm Keihin CV, the Honda Unicorn Keihin 25/6mm, and the old-model CBZ Keihin, with accelerator pump)

The bike had always been a bit of a fair-weather friend:

1. First, vs. the old KB (which would fire on the first kick after sitting for months), the Impulse never wanted to start after being left anything more than a few weeks in the cold weather; and it wasn't the battery... the carb just wouldn't fuel the engine for some odd reason, and I'd either have to pour some petrol in the sparkplug hole or push-start it down a long hill to get it running. Serious PITA, to say the least.

2. In the rain, the rear brake shoes get extremely sticky and lock suddenly on light application... and they don't unlock when releasing the pedal, either, or until the bike is rolled backwards a few inches - very dangerous, a good way to get rear-ended out on the road, or to loose control on slippery/loose surfaces. Springs and linkage fine - it seems to be an issue of lining material.

3. The ceaseless splashing of mud/water onto pantlegs on wet roads (due to high mudguard).

4. And lastly (and most infuriatingly / irritatingly), the apparently common issue of the carb slide sticking in the closed position in any kind of damp weather (monsoon, clouds at Rohtang, sometimes even just cold temps that cause condensation, etc.


I'll just be addressing the last one here, and will start by saying that only solutions on-road were either a swift-kick to the side cover to knock it loose again, or else opening the intake pipe and physically pushing it up. Either of these "solutions" was effective for as little as ten seconds, so suffice it to say, a one-hour trip in the rain could be a real pain. Polishing the slide / installing a new slide didn't fix it, and warranty ran out last month (showroom an hour away, and didn't feel like running there in the rain when it was manifesting, nor spending days down there watching them try and resolve it in dry weather, only to see it re-appear.

Two things here:

1) the original 28mm Keihin CV carb seems to be oversized for a mildly tuned 150cc (foreign-market CRF150F's use only a 24mm non-CV, and Pulsars/FZ's, etc, are using 26mm CV's and have more hp than the Impulse),

2) I think Keihin was pushing their design limits towards cost-cutting, and being that both their 28mm and 25/6mm carbs use almost the same exact carb body and same sized piston, it's evident that there's a lot less material supporting the piston when used in the bigger-venturi 28mm carb... What I can ascertain is that in high-vacuum, off-throttle conditions (coasting / decelerating), the lower half of the piston, being so ill-supported in its bore, gets pulled forward and "cock-ed" slightly, jamming it against the leading upper edge of the venturi. Hope this makes some sense...

To be cont'd...

[ringoism]

.... cont'd from below...

The bike had, moreover, run terribly at altitude in stock form. I'd managed to get it tuned to where it ran pretty well, but it still had its hiccups - occasionally backfiring through the carb, or manifesting weird effects on full-throttle roll-offs. Power also tended to go completely flat under about 3,500 to 4,000rpm, requiring downshifts on gradients.

They say that CV's are more tolerant of over-sizing than non-CV carbs (since the slide itself can't be snapped open, causing bogging - it's controlled by vacuum, and won't open till the pressure differential on either side is "right"). But I figured the 28mm was probably running the slide only very slightly open much of the time, which is not really where it's probably designed to operate best.

I'd picked up an old-model CBZ carb at the scrapyard a couple years ago, just kind of waiting for my warranty to expire so I could play around a little... he, he Think I paid around Rs100 for it...





I remember riding one of those bikes several years ago, and taking note of its better-than-average performance and responsiveness. This despite its having a half-horsepower less than the Impulse at about the same weight. People have attributed this to the accelerator-equipped carb, and I've been wanting to test the theory.

Note in the photos that the venturi is considerably smaller, though on the engine side the opening measures 26mm.






I spent a couple hours yesterday making an adapter that would allow me to bolt it up directly to the original connector:






Carb was cleaned up fully inside and out (fully disassembled):





And upon installation I gave it a try. I'm going to have to order the double accelerator cable, and maybe a 40mm cone/pod type filter, which should fit okay under the side cover. Managed some jugaad with my old KB cable just for stationary testing and it seems to run (idle/respond/rev) well, but let's see how it does out on the road.

And let's see how my fuel economy is affected (not a strong point of early CBZ's). I'd have to give up the throttle position sensor in the process, unless I can find a way to activate it using the existing linkages... which will be tricky as in the absence of a throttle-shaft, there's nothing turning on the left-side of the carb where it would have to be (on the right side, it would send its signals reversed).

Most likely its main purpose is to cut the ignition advance a bit under certain throttle conditions (to prevent detonation, to improve emissions under certain conditions, etc). I've run the bike with it disconnected earlier and could tell no difference in performance, but let's see.


Meanwhile, I'm running the Unicorn carb on its stock jetting, with the Impulse slide-spring and piston (which has bigger vacuum ports in the bottom, probably lending itself to quicker responsiveness).

Preliminarily, I can say that the bike runs better at low revs now - even as low as 2,500rpm it'll pull and transition smoothly. It's equally (or more) responsive, and seems to rev a little less happily to 8,000rpm (I think the 28mm could pull pretty well to 8,500 or more) - all of which I guess is what one would expect. Best thing being that it doesn't stick in the rain anymore (have done plenty of wet riding the past two days).

More later,
-Eric