Re: Hero Impulse ownership experience

I am not even 5'6" and I own impulse. Riding it with absolutely no problem with height, at least for me. In fact soon your bike becomes a part of your body and you adjust automatically to it's dimensions.

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Re: Hero Impulse ownership experience

I thought sales of impulse is discontinued.

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Re: Hero Impulse ownership experience

It did??!

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Re: Hero Impulse ownership experience

My wife is 5'8" and the seat is too high for her to ride - can't even get the tips of both toes on the ground. Of course, not everyone's legs are the same length... so feel free to test one yourself for fit. I'm 6'2" and there have been a few times on rough terrain when even I couldn't get a foot down when I wanted to. I have a feeling this is part of the reason for the Impulse's poor sales.

Having said that, some of the seat foam could be removed, and the fork tubes slid up in their clamps a bit, to lower the seat height an inch or two. Even the rear shocker mount could potentially be modified a bit to lower the rear end. I might be doing all this on another lady rider's Impulse when I get the time. Don't know how tall she is exactly, but even after a year and a half of riding, she's not been able to gain much confidence on it due to the saddle height.

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I see further on in the thread that you've found the problem (the diaphragm); But for the benefit of others who may experience it, will share this:

On my Impulse the diaphragm-operated carburetor slide itself has often got physically stuck in the closed position, causing the exact same symptoms. For some reason it usually happens when it's raining - I suppose because of moisture building up in the carb throat? Must be a minor manufacturing defect in the carb, but polishing everything didn't help. Anyway, local mechanic friend suggested lightly oiling it with light (sewing machine?) oil, which I'll try when I have time.

First time this happened to me I was coming up the back side of Rohtang Pass - not very convenient, to say the least, but I had an idea what it might be, and managed to fix it on the roadside.

For anyone else experiencing such symptoms, easy way to check is to remove the right-side cover from the bike; with engine switched off, loosen the clamp for the rubber tube running from the airbox to carb and pull it off the carb. Looking inside the carb throat, you'll see the slide in the down position - take a smooth-edged screwdriver and try to LIGHTLY lift it up from the gap under the slide to see if it's moving freely. If it seems to require some force before suddenly releasing and moving upwards, it's sticking, and that's your problem. The sewing machine oil (or WD-40, or ???) might be the solution.

-Eric

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Unicorn has a 25 or 26mm Keihin carb (I've physically removed and measured it), Impulse uses a 28mm, so the slide won't be the same. Kind of surprised the CBZ unit didn't work.

Personally, I'm considering converting to the old-model CBZ pumper-type carb. Will take some mods, but no diaphragm to fail and better throttle response (if a bit lower fuel economy maybe) due to the accelerator pump.

If the electrical connection is the same, you might be able to just swap the whole carb for a second-hand Extreme (or even Unicorn) unit.

-Eric

Re: Hero Impulse ownership experience

Finally got a replacement vacuum piston, after nearly 100 days!!! spares are increasingly hard to come by, a friend of mine who owns another impulse is searching for a drive chain-sprocket set for nearly three months, no ASCs near doesn't have any spares for the impulse in stock, it's becoming a difficult proposition to continue using it as an everyday motorcycle if it's your only motorcycle. And to look for an alternative, there isn't any........well, unless you can afford a Triumph Tiger 800

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Well, I've used Petronas 0W40 fully synthetic in my Impulse, the engine felt a bit slower to rev than normal, only a tiny bit, but slower.

Hero Impulse ownership experience

Just hit the carb on the plastic while riding. What happened is that the throttle body just gets stuck half way to the top and it needs some hammering to get back to normal position. It happens mostly while riding in higher altitudes also where the air fuel ratio is not appropriate.

Re: Hero Impulse ownership experience


I'd found an interesting rule-of-thumb somewhere online - may or may not apply to all bikes, but it suggests to:

Reduce main jet size 1% forevery increase in elevation of 1000 feet above 2500 feet.

So having removed the cat and added a foam filter last summer (similar to Ankit's improvements, I suppose), my previously very rich stock jetting (#132) was now actually running just about perfect here at Manali (more air now flowing through the engine to correct what had been too much fuel for a smaller amount of air). So if the bike is properly jetted for Manali (7,000ft) and I'm wanting to ride in Ladakh or Spiti and feel the best compromise would be to have it running "perfect" at an average of 12,000ft, then:

12,000-7,000=5,000 Thus calling for a 5% decrease in main jet size; i.e., 132 x .95 = 125. If I really need more power at the higher passes and don't mind it being a little lean elsewhere, I could figure an "ideal" jetting at 15,000ft, which would then be 8,000ft increase, i.e., 8% reduction, or .92 x 132 = 121.

The formula seems feasible on the basis of my previous experience. When I rode to Ladakh a year ago, the bike still had the catalytic converter and the stock paper air filter, so a #132 had been way too rich even at Manali, showing a black, sooty plug and even misfiring. At that time, a #125 was maybe about right locally, if I remember right (the formula would bear this out, too). I ran to Ladakh and back with a #117 jet and it ran fairly well most of the way, but still misfired on the higher passes (Baralacha/Thanglang La especially), so figured it could've been just a bit smaller still. Well, RIGHT! At 117 I was running eight sizes smaller than what was right locally, which reversing the formula means 117/125 = .94 - so it would've been idealized for 7,000+6,000=13,000ft! Fine at Rohtang, but too rich still for the 16-17,000ft passes. Figuring for 15,000ft would've put me at 125x.92 = (viola!) 115!!!

Hope this might be helpful for others planning for travel at higher-than-normal altitudes. Don't take it as "law", but something to experiment with.

Thanks,
Eric

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Anyone else out there experienced a distinct mechanical rattle in the engine at particular rpm's?

It started in mine not long after the 6,000km service, and occurs predictably and consistently at 3,000rpm and again at 4,500 till 5,000rpm's at anything other than light throttle/load.

Kind of sounds like looseness in the connecting rod, honestly, but don't know how that would be so on such a new engine. The rest of the rpm range is smooth/quiet.

Lest anyone think I've ruined the mechanicals with all my risky fiddling (and/or hard riding), let me say that I heard the same sound in a completely stock, lady-ridden bike I borrowed briefly last year - it had something like 11,000km done, if I remember right. The sound was alarming then, and it's alarming now. I ride a somewhat neglected, ill-maintained Unicorn on occasion that has more km's done, and is still absolutely quiet down there. And this is essentially the same engine, so this was most unexpected.

Any help here appreciated.

-Eric

Re: Hero Impulse ownership experience

Has anyone changed tyres on impulse and at how many kilometers? Yesterday I felt that something is wrong with my tyres. I stopped at a puncture wallah to check the pressure. He told me that your front tyre is punctured and it has only 10 psi air left. I don't know why it was not flat. He put two patches inside the tyre and when checked tube in water it showed many holes. So 400 rs for patches and 450 for a new tube . I still wonder why tyre tube was not flat with 4-5 holes. Air pressure was around 10 psi when checked before opening it. Was I cheated? And if tyres are gone bad then I seriously doubt ceat for quality because 15000 kms are not enough for a tyre to go kaput.

Also is it OK to put 3.25/19 bullet front tyre size tube in a 90/90 19" impulse front tyre?

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Re: Hero Impulse ownership experience

Sounds fishy. Did you inspect the inner side of tyre for nails or thorns? If anything is stuck then it can lead to multiple punctures. Leak might be slow.

I think you can put new tube n use existing tyre after inspection of inners.

Regarding Bullet tyre, 3.25 is slightly smaller than 90mm. You can put that but good to find stock size.

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Re: Hero Impulse ownership experience

A local mechanic who is a friend, i share a good repo with him, told me that it's a common practice by puncture wallahs to increase the punctures in your tube and they do it so efficiently that it's very hard to catch them. There is a puncture shop just adjacent to his workshop. And I am sure that I was cheated.

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Re: Hero Impulse ownership experience

Yes, looks like he made a quick buck with your tube. However, your tyre seems to be the culprit. I had similar experience with my RX 100 front tyre. I check the pressure every week and every time it will hover around 10-15 PSI, though I would have filled 25 PSI the earlier week. If the tyre & tube are weak this is a common thing to happen.

Re: Hero Impulse ownership experience

Aah...sorry for the late reply. Got tangled up bigtime lately..anyways.

Small window carved out for the removal of the cat.


Getting the CAT out.


This was the rear baffle tube at the end of the canister, with again lots of glass wool and unnecessary restrictions aiding forward to more restriction.


Now as per the exhaust header (bent pipe) its even more restrictive as double tubes run in the small 18mm header. That`s gotto be fabricated later.
Anyways....as far these mods are concerned low/mid end has improved marginally...no hiccups and the mill is breathing more easily. having the baffle removed has got the bike a little flat sound, very subtle as a dirt bike, somewhere less loud than the Duke 200 in audible terms i`d say.

Re: Hero Impulse ownership experience

Even im circling in to somewhere near 115 jetsize. I doubt 118/120 will get me through 15000+ft passes. 125Jetsize had its potency going great till i hit 12000+ft last week. Having done with the 125mainjet after down-switching from 132jetsize, and observing a significant gain in heights where the mill can stay running good [7500(where it barely climbed) to 12000ft (almost)]. So gaining heights now (for Ex: 15000) will take somewhere around 120jetsize...(going by the measure of the hypothetical equation i'd say) Quite nicely described in that formula of your's ! I downsized and i gained heights. But now doing 17/18000ft will take a couple of more downjetting (if jetting is the only thing to be focused upon). But keeping in mind how the air decreases with altitudes is not linearly but geometrically. Air what decreases in 12000-13000ft will decrease thrice as less as what will in 15000-16000ft. So oxygen levels decreases geometrically at heights at a higher rate. So downjetting to somewhere around 115 or so will be fine i guess. Thats ive got till now.

And as per engine noises 17k on the odo and my tappets have loosened gotto get them rectified too.

Re: Hero Impulse ownership experience

I had some nasty misfiring at points at ThanglangLa, but did get through to Leh on the 117. It would better on the 117 now, with the subsequent air filter/exhaust/main needle mods (see below), which would lean it a bit more.

Trouble is that if you haven't lowered the main needle in relation to the slide, you will still have trouble (like I originally did) regardless of which jet you've got, since the jet we're changing is the high-speed jet, which exhibits most of its effect at 3/4 to full throttle opening - and (deceptively) on a CV carb, the "actual" throttle opening is really the amount of slide opening (not the butterfly valve your cable is connected to) - since this slide doesn't open (vs. an old conventional carb) with your cable / twist grip, it opens with vacuum - which is a lot trickier thing to control / monitor up there.

So in my case, IF and when I got the vehicle speed up enough, and the rpm's up high enough, the thing ran GREAT with the 117 and I was blowing past Karizma's and RE350's and everything else even on the highest passes, and showing perfect plug color, because the slide was fully open and the full effect of the high-speed jet came into play. Trouble is that anything short of 3/4 opening of the slide, most of the effect actually comes from the needle height, since the actual flow area = needle jet CSA - needle CSA at that particular part of its taper.

That's to say that when the needle is fully raised, it becomes irrelevant since the flow area between it and the needle jet is huge and the high-speed jet is the only limit to flow. Less than 3/4 opening, it's the high-speed jet which is irrelevant, since the flow area between the needle and needle jet is less than that of the high-speed jet.

Long story short, if you want to lean the mixture for anything between about 1/4 and 3/4 slide opening, the only way you can do so is by restricting the flow of fuel by moving the needle down, so that it's a larger diameter part of the taper restricting flow through the needle jet. The high-speed jet (be it 132 or 115) has much less effect in this range than the needle height. Unfortunately, needle height is not height adjustable using the clip/slot system that older carbs had, so you've either got to retrofit such a needle or modify the stock one as I have outlined in my Tbhp thread.

I was a little beyond Pang on the return from Leh when I finally couldn't take the low power and misfiring (at anything but high rpm/full throttle) any more, and on the roadside pulled the carb slide / needle out, and filed off enough of the needle's upper flange to lower it a bit in its mount in the slide. It ran much, MUCH better after that!


Re: noise, Unfortunately, my engine's noise is not from the tappets, which make sounds much less related to load or rpm-related as this clearly is. Really sounds like detonation, which would point to too-aggressive timing advance from the ignition module (feeding in either excessive or too-early advance at 3,000 and 4,500 rpm respectively), but since the sound wasn't there earlier, it also suggests some loosening of either piston or rod clearances as well.

Very tempted to see if the electrical connector on the Unicorn/Acheiver's module is the same, and if so swap one in as a test; if it got quiet, I'd know it was the timing curve to blame. If not, I'd know it can only be resolved with some attention to the engine internals (but why would they be loose at 6,500km?).

Thanks,
Eric

Re: Hero Impulse ownership experience

Great ! That needle positioning will surely help. Also a 26mm Unicorn's carb with a simple swap on the Impulse is what im thinking forward to, but hard to source and test it over high heights takes a lotta time and money to spend upon. Meanwhile running this needle drop by shaving the flange top a little is a good idea going by no slots at needle top alike old carbs (which could have been more handy) is pretty appealing and will turn lean the mixture a lil more.

Had few worl done on friend's Impulse last week with cat and baffle tube removed and the foam filter installed...carb issues are yet to be solved on my bike. He asked for the 125mianjet which is on my carb...fine it would worked but upto an extent. So phasing out that option and as he was aiming for Sipti and Kunzum we had the 132jet wired for the meanwhile.