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|3rd July 2017, 11:19||#91|
Join Date: Oct 2004
Thanked: 66 Times
Re: Replacing the KB-RTZ offroad specials - My Hero Impulse
The Impulse brake shoes wear out rather quickly and they are hard to source. The Hero Splendor rear brake shoes are fortunately a direct fit though and cost less than a hundred bucks.
|29th September 2017, 01:02||#92|
Join Date: May 2012
Thanked: 1,115 Times
Re: Replacing the KB-RTZ offroad specials - My Hero Impulse
BRAKES: When it came to the sticking (which was there particularly in damp/rainy weather), what I needed to do was to disassemble the brakes, remove the shoes (still plenty of lining there), and the actuating shaft, which I found to be absolutely dry / devoid of lubrication. Greased and reinstalled, roughed up the brake shoes with some sandpaper, reassembled, and they were better than new. Hero must've forgotten to grease that shaft at the factory. It truly was bone-dry, as though it'd never had any lube on it ever. Brakes are perfect now.
CARB: In other news, have (permanently, I think) swapped in the Unicorn 25/26mm carb (basically a direct-fit) after having modded the throttle slide by adding an extra vacuum port in the bottom (Impulse had two originally, the Uni only one). I felt it superior to what I was getting with the CBZ pumper-carb, whose loud, crackly pod-filter sound I also detested vs. the Impulse's airbox's slightly modded, deep and throaty roar. And I must say, the performance improvement over the original is very noticeable. A lot more low-end grunt, very responsive, without seeming to have any significant loss on the top-end. Probably could still perfect my jetting a bit, but it isn't far off. The formerly irritating 1st-2nd gear ratio gap is a lot less pronounced now, as a result. A LOT more fun to ride this bike now, just because I don't have to rev it like mad to keep it moving along. Uphill, it used to lose power below 4,500rpm, and fall absolutely flat below 4,000, requiring a downshift. Much, much better now, down to 3,000 under the same conditions, or sometimes even lower. Just great. The original 28mm Keihin was just ridiculously oversized for a 150cc bike, and though CV carbs are more forgiving re: mis-sizing, there must be limitations. Old carb was the second thing (besides the rear brake) that used to stick in damp/wet weather, and this Unicorn carb doesn't ever. Couldn't be happier. I just spent about 13 hours on-road in some very vigorous hill-riding down to the plains and back, including some time on some very bad/broken/gravelly stretches; the bike managed 44kmpl on the way down, and 38kmpl on that very brisk, throttle-happy (50kmph average speed), nonstop run back, with a lot of uphill (a couple km's straight-up climb in altitude).
21-er wheel: Thirdly, finally got around (six years after I had it plastic-wrapped at the airport on the outside of my suitcase (since it wouldn't fit inside)) to lacing up and installing the 21" front wheel, complete with the "Golden Boy (a.k.a Shinko) 244" 2.75x21 tyre, quite a well-rated tyre abroad, which cost me under $30 U.S. Great performance dirt cheap - can't go wrong there. The original CEAT still had tread, but horrible cracks in the sidewall (which had started not long out of the showroom) had already produced three or four sidewall punctures in the past 18 months, most inconveniently en route to Tso Moriri on dark night...
I'd brought the rim, and a friend the tyre, over here long before the Enfield Himalayan intro'd 21's to the Indian market (they were plentiful in Nepal from long back). I'd intended it originally for the offroad-modded KB-RTZ, but never could find (or get made) the right length spokes to mate the bare alloy rim I'd brought to my original Bajaj brake drum; And then I bought the Impulse in the meantime. Always felt it would be about right for the latter, comparing it to similarly sized/weighted bikes abroad, but same issue with spokes. Used a spoke-length calculator to figure out what I’d need, but the places in Karol-Bagh who could make them wouldn’t do a batch of less than several hundred, which of course I’d never be able to use. Could’ve sourced them from China, but doubted the quality and they were expensive vs. what spokes cost here. Figured out (from the spoke length calculator) that if I laced the wheel “1x” (note photo)
instead of the original, standard “3x”, I’d be able to use the original spokes from the Impulse’s 19” wheel on the 21”. Sourced a new set of spokes from Hero, but they never could get the nipples, so that held me up another year or more. The original KB spokes have the same 3.5mm nipple threads, and finally I had to buy a box of 100 spokes from a Karol Bagh supplier (only Rs200) to get them. Laced it up and trued it last week, and finally got it mounted up a few days back. Some doubts as to how it might, with this alternative lacing, over-stress the hub, and so won’t recommend this to anyone, but am currently testing it. In three days, some rough roads, so far, so good!
I was unsure enough about how it would work out that I didn’t want to disassemble the original Impulse rim. As it turns out, the Pulsar hub is dimensionally the same in terms of the spoke-circle diameter, width, etc. Trouble was that the Impulse disc-mount attaches to the hub with five studs, whereas the Bajaj uses six… something I didn’t realize till I actually tried to mount it. Fortunately the Pulsar disc is the same diameter / spacing from the hub as the Impulse’s, so I was able to just use the entire hub/brake assembly from the Bajaj; the caveat being that the disc is thicker, and thus if I had fresh, thick brake pads in the Impulse caliper, would not fit between them. Fortunately my pads are half-worn…!!! :-) I’ll have to see about a thinner disc that will mount to the same spacer/hub. I’m going to guess maybe one of the Discover models would have one. A petal-type would reduce weight considerably vs. the thick Pulsar unit, as well.
1) Softer ride, perhaps as much from the newer, softer, thicker tread as from the increased diameter;
2) Definitely handles perpendicular sharp edges of potholes, abrupt curb / drain-like obstacles better / smoother. I could ride over logs with this thing.
3) Bit more “gyro-effect” which is to be expected. It isn’t going to turn as quickly, but it feels very solid / planted, both on and off road.
4) Geometry would’ve been effected a bit (more rake angle), also contributing to this effect.
5) More ground clearance, which will increase even more if I could get the original 110/80 back on the rear (or better the Himalayan’s 120?/80) vs. the MRF Moto-D 100/80 that was the only thing available when I was forced to replace pre-Ladakh-ride. This would get the geometry back to original, as well.
6) The gloriously named Korean “Golden Boy” grips the edges of pavements and any loose / slick stuff much better than the original CEAT, which was really more of a road-oriented tyre. I think that once I’m accustomed to the slight handling differences, I’m going to feel much more confident on this than on the original (quite a number of my spills on various bikes over the years have been caused by the front tyre washing out on turns when pushed too hard). And surprisingly it isn’t as noisy as the CEAT either. Seems just fine on-road, though I haven’t tried to push it yet.
7) Headlight aim is high, and not enough adjustment to get it as low as it should be now. With the 55/60W installed (great upgrade in itself, which I will also not recommend as I’m not sure it won’t degrade the reflector / damage wiring / switchgear in time), I am blinding oncoming drivers, something I have always hated to have done to me and have always sought to avoid doing to others (the Golden Rule there). Going to have to disassemble the front fairing and see how I can mod the mountings or whatever to get it aimed right.
8) Looks: Well, the MRF rear tyre was already looking a little slender vs. the original, and having this 21” proud, anodized aluminum unit thrusting itself out front hasn’t helped at all. Really need to see if I can source something taller for the rear (4.10x17 IRC / Duro of same tread pattern would be great), and preferably a matching alloy back there, too.
9) Mudguard clearance: I’d had doubts, but no issues whatsoever.
Overall I’m satisfied, and would consider this a worthy upgrade for me considering my usual commute…
Some may have wondered whether the Himalayan rim could be likewise adapted and of course it could, but I’d have concerns about its weight and the potential to unbalance the bike, being that it’s a steel unit. Even more so if the RE hub is also used, which is a lot more substantial too. On offroad bikes especially, keeping unsprung weight (tyres, rims, brakes, spokes, and anything else not supported by the suspension) to a minimum is highly desirable.
I'd still like to have a softer / adjustable rear shocker, and the rear tyre sizing is too small now... and I'd like to fit a free-flow silencer and maybe mill the cylinder head for a better compression ratio... but as far as the bike's more irritating quirks are concerned, they've pretty much been resolved now, and I'm finally feeling like the bike is getting just about sorted out. It only took three years!!!
Last edited by ringoism : 29th September 2017 at 01:32.
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