IIRC ZMA stock piston and OS piston are made by USHA.

By the time I heard you mentioning USHA, I had already given it to the lathe. It was not USHA but some other brand. I guess I'll give it some time and see. I asked my mech also yesterday evening and he told it should be due to heating and should resolve over time..

Might have to ride to Masanagudi this weekend. Will be around 600km over two days. I was thinking that I'll change the oil. Should I stick with 20w40 or go for a higher w50? Will take loads of breaks for the bike. Hope all goes well!

Over time the bore to Piston clearance will increase and then your problem will go away..Stick to mineral oils since the engine wear will be slightly more in it and will allow engine to settle down quicker. Stay with 20w40 which offers the optimum performance and protection....20w50 will be too thick and engine will labor to build RPM, hence not advisable.

As PSR sir said , 20W40 is more than sufficient for long rides.

Thank you!

My friend, then you are not aware of the recent happenings. From 2008 onwards till 2011 pistons were changed to SAL(sunbeam auto limited) which although ran good in factory fitted engine. But when replacement bore kit or o/s pistons were used, caused a lot of problem. This was not only case of karizma, but also from splendor to extreme and all bikes. Even i have suffered from this problem when i second time changed bore kit at 2.3 lacs in my joy. Then when the replacement bore that i used had SAL pistons. These kit consumed more oil than before overhauling. Just after 2k the bore was opened and new rings fitted to the piston. this took care of the oil consumption but still the bike felt better before overhaul than now. Then at 15k after overhaul the block seized when i was on a trip. However i completed the 500 km trip successfully. Then the engine was re-bored with MAHLE pistons(was sourced through my retailer friend to not get fake). That idiot who bored the block, kept it so tight that, in morning when the engine was cold, the engine had so much compression that on new clutch the kick slipped. the bike will shut down just like MAXZMA. then after 5k the clearance increased and everything was ok.
Then the block that seized showed its effect after 10k. Due to seize the crank pin had taken the stress and thus con rod sound came. Then i opened the engine once again completely and saw that the clutch side of crank pin was worn. Again new rods and pin was installed, and the bore was also worn at one side as the crank had worn the bore.
Since i was bored of improper piston expansion, so i decided to go for new bore kit, but i had already seen the new bore problem and still the OE bore came with sal pistons. Then my Retailer friend ordered USHA bore kit which came with usha bore,pistons and rings. It has been 35k after install and no oil consumption,compressor is very high and also bike feels like new.
How did i get USHA idea? My bike came from factory with USHA pistons which ran for 1.3 lac without any problem, then the first replacement kit also came with USHA and it ran for 1 lac without a hiccup. Now my mechanic always uses USHA pistons and nothing else. I researched a bit and the japan pistons that came prior to 2004 were USHA. Since USHA supplies after market i went to USHA.
After repeated complaints from consumers and service centers the OE bore kit supplier was changed to USHA from SAL in JULY 2011.
So you see with so much experience on block piston, the problem when he mentioned, i immediately came to know that it is a case of different piston and not USHA.
Let me tell you splendor pistons by MAHLE AND GOETZE cost only Rs.400 but the piston from USHA cost Rs.700. It is because they are made by semi forged and also 11% silicon is added which guarantees there performance.Even USHA makes valves, but USHA is pioneer in diesel vehicle parts.


I knew as your problem is what i faced. See i work on my own on engines, even though i sometimes give it to mechanic, but then also my mechanic always calls me to inform me about proceedings and i also get spares.
Use 20 W 40, after riding 50-70 km, stop by road side and check if engine is idling normally, if yes then continue, else give some rest. As soon as you see engine is giving problem, then give it 15 minute rest.
When my engine has seized as mentioned above, I did the same. If my bike would rest then it would pull to 80-90 with two up like crazy and once heated will not cross 50. So i used to take breaks. Since yours is not seized and recently bored so take care and do not rev over 6k.

Ha!!! That makes sense!!! My bike was purchased on July 2011, and just within a month of purchase started facing issues of overheating and the bike made weird noises when hot. Every mech I met including the SVC people said that it was normal, but I put my foot down and demanded to open up the block, and there you have it! The bore was pretty scratched up, the bore kit was replaced and I remember asking the mech the reason and he said most 2011 ZMA's have this issue and have come up for cylinder kit replacement, and on inspection I remember seeing USHA(Paid attention cause we have a sewing machine with the same brand name and I was wondering whether its the same manufacturer. ) on one side and some 2 digit number as well, in the bore it was written KRY. The reason for partial seizure was that the piston pin had scraped the bore wall. I didnt get to check the manufacturer name on the stock piston, cause back then I didnt know much about these things.

@Sibun - Are we getting Usha bore kits for ZMA these days? This information will be useful for many who intend to change their bore instead of risking with rebore jobs.

@sibun - thats a lot of useful information. The question is, in case we have to do engine work now, will the service centre have USHA parts? Can we specifically ask for that? Or should we look outside for those parts?

Asked Arun bro, a few months back he had purchased a cylinder kit, and he said the piston had no brand name written but the bore had SAL written on the exterior.

I just checked mine and its written "D2 SAL" on bore, but my piston is USHA with some numbering. For checking your bore make, check under the fin from the kicker side of the bike.

I remember seeing a KRY on the piston..

I believe KRY means Karizma, cause on the other side of my bore there is KRY written.
And IIRC ACS Sir's stock piston had USHA written on one side and KRY written on the other side.

By default speedos aren't accurate . And errors on speedos differ in different bikes .
You can do a speed check with a GPS enabled mob.

Sir , with the inevitable speedo error , won't it show above 130 kmph if he was going at 8500 rpm ?
@Ashwin - seems the piston was USHA .



Was away for some time ...some personal matters and an HVK AIM at Wayanad . Met some guys there including AARGEE ( Ganesh Ramachandran) .

Finally got new carb!
Bad news, jettings screwed and only runs with choke and emits smoke, with half choke back fires from intake.
Good news, bike revs till tacho ends i.e 10.25k.

??? Details ...