Re: Problem solved

yes actually that cylinder never had ring in it. The mechanic told me later on. That's why that clearance was there. Then I shouted on him as I never knew but yes it was his fault he should have shown me before hand that sir it is without the rings that's why the gap would be there.

When the company's person came he came with a new cylinder kit he fitted the rings inside it infront of me and showed me. Just to make me satisfied to see where is the gap.

Anyways the problem is solved.

Re: Problem solved

With due respect to Honda engineers,the right way to check the bore is to check it with the piston inside it, without the rings being installed.If there's no daylight visible between the piston and the bore,then that bore kit(bore with piston) is considered as ok.Then you have to tap the piston gently to see whether there's too much piston slap as well.Both these tests have to be done at different positions in the bore.

Re: Problem solved

I fully agree with our gixxer bro. Piston should have 0.20 mm gap between bore and piston without rings. For easier way to find out a piece of paper from a standard notebook can be inserted and nothing more. This is problem with new HONDA UNICORN and shine.

I have heard 2 shines straight out of showroom having crank sound. Also most shines are smoking in 30-40 k. This was not the case with the old shines. But from 2010 onwards i am seeing this problem. My friends Uni started smoking at 50k. The bore kit was replaced in showroom and after 1k bike started consuming oil. Then he came near me, when i opened the bore the piston has as much free play as your photos and piston was covered with oil as your photos. I then went to my mechanic and he said that all new bores come like this. Only solution was to Bore out or install new bore kit of achiever, we got a first oversize USHA piston and went for boring on boring and honing machine. The bore after boring was so tight with new piston that we have to push it to move, that too without rings. We have it installed and till now he has run another 50k and still no problem.

What Honda is doing is that it is keeping more clearance between piston and bore and rings is what seals the bore. The result is that bike feels free out of showroom, no special need of running-in, and also mileage is more. AS friction is less mileage is more. But the problem is after 10k the top end will decrease, engine will consume oil in small quantities, and what not, also piston slap will occur.

Now do not think me wrong but previous model unicorn(spoke wheels), shine doesn't suffer from this problem, even i feel the new activa will face this problem. Ride a new bike from showroom both Unicorn and extreme, you will see the unicorn will feel smoother and more free to rev than extreme, but after 10k extreme will rev freely and quite fast. Even my extreme took 10k for it to completely open up and mileage also increased slightly after that.

The video that you have posted it looks like a standard piston is sliding in an oversized bore. Your old piston which has run only 1k shows severe oil burning which clearly indicated that oil was seeping into the combustion chamber. This is the case with all shine,unicorns. Also you will hear the crank sound at only 40-50k. Believe me as i have opened a lot engines alone and also with my mechanic.

Even our stunner is feeling like that it is having much less compression than my extreme, i am not comparing it with my Joy as it will feel like no compression with my JOY. May be after another 5-6k i will see that what is the positon of the compression. Its because the stunner is feeling lazy to rev, although mileage is good at 62-65 kpl. Earlier the bike was feeling free to rev.

So the solution is to bore using boring and honing machine, and use 1st oversize USHA piston, get an acheiver bore kit or sell the bike and get another bike from other companies.

Re: Problem solved

Great info ! If this is true, do not know why Honda is doing this ...when they know that at end of day, bike is going to give problem.

Re: Problem solved

Honda is not doing this but public is wanting this. Now you may ask How?
It is because public wants a bike which will be smooth,return more mileage and can rip straight from showroom. SO what Honda did was decrease the friction even in new engines. It increased the piston to bore clearance as in new bore if piston expands then skirt will rub against bore. Running in is basically subjecting piston to heating and cooling cycles so that it will never expand again thus preventing seizure.
2. Second thing Honda did was increase the clearance in big end bearing which was good as crank rotated freely. But the downside is that on running the needle bearing will wear and will cause more play.

The ECO thrust that is now advertised is this method in which crank and bore are free and thus return great mileage.

You will not believe that when i bought my extreme it returned 35 kpl. My friend commented that his UNI returned 60 kpl straight out of factory and this one so less. But after 2nd service the mileage increased to 55 kpl in city and 60+ on highway if kept below 60 kph.

Similar is the case with my fathers splendor, when new returned 50 kpl after 2-3 services returned 80+ kpl. All these even without touching carb.

In my joy, when it was new it returned 55 kpl. After 4 services it went to 80 kpl. Today engines of hero are still free than earlier as my joy when new was so tight that if a small stone is under rear wheel and you are starting to move then bike will not move. Kick was so hard that unless you shift it to half position by clutching, you cannot kick it.

Even when i re-build the engine of my Joy it requires almost 7k for completely freeing up.

Even my extreme after completing 10k has become free. Now it is at 14k and revs like crazy.

Re: Problem solved

Honda calls the new tech.. LOL. We have been doing this with our rx for ages so that we could rip them from the word go..

Honda is destroying their own reputattion for reliablity by doing this.

You are also right about people's attitude towards running in. I have seen many new bikes, in the garage i get my work done, doing nothing more than 7-10k kms, coming for engine noise, crank damage, main bearing sound, clutch slippage etc...

Most, when asked, have the same reply, we bought the bike. We ripped it from day 1. We can ride it any way we want and the bike "SHOULD" withstand it. Honda is just giving them what they want. The number of informed riders who are willing to take care of their rides is very few compared to these kind of people.


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Re: Problem solved

Wow then I'm lucky to have the first gen uni, its 42k km used if I require a new piston bore kit so this is what I'll get from honda or should I use hunk or extremes kit?

Re: Problem solved

Mine also same like your bike model. It was slightly smoked at 87k. I just bought 0.25mm oversize Usha piston rings and re bored it.
Now it crossed 100k, the compression and top end like new bike.FE is always between 56~58 range. You can follow same method and no need to go for new bore kit.

Re: Problem solved

If you can get it bored at a reliable ledh shop then go for it. Otherwise go for a hero bore kit. They should be of better reliability as they dont seem to use this het concept.

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Re: Problem solved

Hero seems to be a better option

Re: Problem solved

[QUOTE=sinnerz2000;961012]Hero seems to be a better option[/QUOTE

If you cant get it rebored with a xtreme os piston then yes.

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Re: Problem solved

[QUOTE=Bibhu;961014]What is done in reboring exactly? A port is to increase the bore size and add a bigger piston right?

Re: Problem solved

[QUOTE=sinnerz2000;961040]In reboring the bore size (effective piston diameter) is increased, generally by .25mm so that the block can take the next over size piston. For example unicorn/extreme's factory bore size is 57.3 mm. So the first oversize should be 57.3+.25=57.55mm. So the block diameter would be increased to 57.55 mm so that it would take the 57.55 or first over size piston.

Porting is a different matter altogether where the ports through which the intake or exhaust gases travel through are reshaped in order to achieve more power/efficiency.

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Re: Problem solved

Its great to read your posts ! You are right that people want to rip bikes straight out from showroom. Have seen numerous brand new activas/Hero passions/Discovers and what not....being ripped like crazy !! There were instances when I saw brand new activas with three people on it and being ripped like hell. Poor scooter. General public does not even know terms like " Running in" ! I mentioned about running in to few of friends..... and they were blank !

Re: Problem solved

Its sad to know these ppl have no respect for their bikes, ppl treat them like dirt nd then whine later when the engine gets messed up.