Re: Honda Unicorn

Your bike is clearly burning oil as even after using so much thick oil like 20W 40 your bike is consuming oil.Most of the new unicorns start consuming oil at 40-45k mark as Honda has given less tension rings to increase mileage and smoothness. The side-effect is that after some kilometers of running bike will start consuming oil and also will struggle to reach top speed.Nothing to worry, but do this immediately or else bore will get damaged and then crank and you will look for a fatter bill.1. Open the bore and check the ring for gaps. I am sure they will have gaps way beyond permissible limits.2. Get a 0.25 size ring set. If possible get one from extreme as they have more tension than unicorn rings.3. Take the bore, piston and new rings to lathe and ask them to grind the edges of rings so that it can enter the bore without overlapping edges. Grind it till the ring gaps in bore comes to 0.05 mm when inserted inside bore. A rough indication is that when you look at ring in bore it will look like no gap but when viewed against light light will pass slightly through the gaps. Do this for all rings.4. After getting the rings back slightly rub the edges of rings with a small file to smoothen out the rough edges after grinding. After smoothening out the edges with small file use sand paper to further polish the edges that have been grinded.5. Now clean the piston and specially grooves to remove any carbon properly.6. Fit back everything and use new engine oil of recommended grade. Follow a run-in of 500 km as these rings will be very tight, even more tighter than new bore kit.DO this as soon as possible else will have to overhaul complete engine.

Re: Honda Unicorn

Hi Sibun,

Thanks a lot. My Bad luck. I am seeing your reply only now.



Just a background of what happened:

Bike has completed 39000 Kms. Today bike stopped all of a sudden on the way back from office (Thank God, it ran without issues for 49 Kms from office and stopped 2 Kms before my house).

Checked with Mechanic and found that Valves are bent. Engine head was removed and the following parts were procured

Bike Valve set and Valve Oil seal - 400 Rs (Honda)

Rack ram adjustor (2 No) - 540 Rs (Hero Make)

Packing Kit (washers) - 50 Rs

Paste - 30 Rs.

Went with Mechanic to Lathe shop for replacing cam shaft bearings as there was some free play (left to right)

Lathe guy informed that the Valve guidance (small tube like part attached to the head) was also having some issue.

The new Valves were not moving freely through the valve guidence and was stuck at some point.


I was asked to change the valve guidance and also cam shaft bearings. Cam Shaft was good and did not need replacement.

Lathe Labor and parts - 650 Rs.


The Lathe guy saw the carbon deposits on the head and told that re-boring may be required and told the mechanic to remove the bore and check.
He suggested to get a new bore kit or re-bore the old one so avoid any engine problems in the next 20000 Kms.

We removed the Bore and removed the Piston

Piston Rings (5 Nos) were removed from the Piston

Thick Carbon deposits were found on the Piston which can be removed using a blade before assembling the engine back.

The Piston had a free movement in the Engine Bore (with rings removed). I could see a significant gab between the Piston and the Inner walls of the bore. Could see light passing through the gaps but cannot find gaps when looking at a normal angle.


My Questions:

1) Do I need to get a New Bore Kit (costs 2.5K approx). If So what are the other parts which needs replacement to compensate the new bore kit. I assume a used part cannot go hand in hand with a new part

2) Do I rebore the old bore (Costs half of procuring New one). Will it be reliable. I do not want my bike to stop at wee hours with engine problems.

3) Do I just change the Piston rings assuming that it will cover the gap between the Piston and the Bore as per your recommendations.


I am going to Lathe guy tomorrow to check the condition of the bore.

Your suggestions will highly be helpful.

Re: Honda Unicorn

Its best to replace the bore kit completly as reboring is not reliable, you can use cbz xtreme bore kit which is better than honda bore kit( sibun will explain why) and costs cheaper than honda too, it costs 3.2k for bore kit of xtreme which includes the bore, piston, rings and the gaskets.

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Re: Honda Unicorn

As i said almost all unicorns and shines require top end work after 40-50k so nothing new.As for valves getting bent this is a common problem as the valve guide is the cause for it.The valves guides of unicorn and extreme cost only Rs. 37 or so but splendor valve guide cost Rs. 68 each. So you can imagine the quality.Change the valve guides with OE or extreme guide. As for the camshaft if need be change with OE and never with extreme as your bikes performance will go for a toss.Re-boring is a good option if the boring guy does the boring with boring machine and honing with honing machine, then it is better than even new bore kit, but hardly most lathe know how to get the work done. So better replacing it and getting peace of mind.As [MENTION=42743]sinnerz2000[/MENTION] has said get extreme bore kit as it has tighter clearance and has better compression and also rings are very hard as a result it doesn't leak compression after running some kilometers.

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As i said almost all unicorns and shines require top end work after 40-50k so nothing new.As for valves getting bent this is a common problem as the valve guide is the cause for it.The valves guides of unicorn and extreme cost only Rs. 37 or so but splendor valve guide cost Rs. 68 each. So you can imagine the quality.Change the valve guides with OE or extreme guide. As for the camshaft if need be change with OE and never with extreme as your bikes performance will go for a toss.Re-boring is a good option if the boring guy does the boring with boring machine and honing with honing machine, then it is better than even new bore kit, but hardly most lathe know how to get the work done. So better replacing it and getting peace of mind.As [MENTION=42743]sinnerz2000[/MENTION] has said get extreme bore kit as it has tighter clearance and has better compression and also rings are very hard as a result it doesn't leak compression after running some kilometers.

Re: Honda Unicorn

I Thank you both for helping me in this regard.

I am unable to source a new bore kit due to a small financial crisis(Married men will know ).

Had to think a lot before I told OK to re-boring (Next Piston size compared to Stock).
3.7K is the cost of new Honda Unicorn Bore kit with Piston and Rings.

Apart from the 650Rs which was charged for Engine Head, Re-boring costed me Rs1000 including a new Piston and rings.

As suggested by Sibun, tried for 0.25 piston rings but the bore was worn out un-equally. Gap between the piston and bore was inconsistent. ie: we were able to move the piston horizondally inside the bore at some places.

Seems The lathe guy is very professional. I stood for around an hour and could see 3 people coming for re-boring. He told that he re-bores 10 engines a day.
He also told that he will give guarentee that it wont fail for next 2 years provided i maintain a run-in period (Max 45KMPH @ 5th gear) of 2000 Kms.


" A small question is iching me. Y did the bore fail when I changed oil at 2000 Kms regular intervels and did a sane riding after from 12000 Kms till date.

Might be because of the run-in I followed earlier ? If So, I regret.

First bike. can't help.
(Believe it or not: Crossed 115KMPH mark on first week and 300 Km round trip highway ride at high speeds before first service) "

Let this be a lesson learnt for new buyers.


Once again, Thank you for listening to my long question and giving suggestions to solve the issue.

Will update once the engine work is complete.

Re: Honda Unicorn

Hi guys back after a really long time to this thread. . . Firstly, let me go with my updates,

1. New shock absorber for the rear, the bike feels good now. . .
2. There was a loss of power and the bike never used to go past 5k rpm but soon was solved, thanks to [MENTION=32286]psr[/MENTION] sir. . .
3. Really proud of my bike, did so much hard core riding, took steepy hills with little stress but never gave away anywhere, even with me and a pillion, off-roading was great. . .
4. Zapper Vyde is just awesome, they say it's a soft compound tire but took it to the extreme on off-roading and eh nothing happened, even though mine's already 10k+ old. . .
5. Going to change the whole diaphragm set next time as it's almost gone, used fevistick last time to glue the rubber into it . . .

So I have these queries now. . .
1. Even though I installed a new shock absorber, I still feel the rear wheel wobbles and it's noticeable at good speeds, say above 70kph, when I just make the bike to wobble, I feel the rear wobbles more, what problem is this. . ? At the beginning of installing new shocks, it was all good but now it has returned, was it due to my off roading. . ?
2. I have been saying this for quite a while but I am clearly not sure about this, . . See it's like I am planning for a new handlebar, kinda bored or say over used to the present shogun's handlebar, I need a change. . . Should I go for a Clip on set. . ? What effects will it have on handling. . ? Will it improve my cornering abilities much more. . ? Planning to go for the nearby lone hill to test my skills for cornering in another week or two, so what you think of clip on sets. . ?
3. Will it look good, again asking as considering that my bike has spoke wheels. . .
4. If ever I would go for a tire change, should I go with Zapper Vyde itself or should I try MRF Meteor-M, dual purpose one for better handling and cornering abilities. . ?
[MENTION=42743]sinnerz2000[/MENTION] and [MENTION=28527]sibun[/MENTION] please pour in your views if you have some. . .

Thanks in advance, will be back with updates soon. . .

Cheers!!!

Re: Honda Unicorn

Welcome back. For wobbly rear Tyre check for axle bend, spokes bend and swingarm bend also check if the tyre is worn out unevenly. For handle bar I haven't seen a clipon set for uni yet which doesn't touch the tank, you can go for fz handle bar which will fit directly without any issues. For Tyre if you're comfortable with Zapper vyde then use that itself or go for mrf meteor, the meteor m isn't good.

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Re: Honda Unicorn

As I said, the bike was fine after it was fitted but after I did a 300 kms ride one day with a pillion which consistent some 50 or so more kms of just off-road, worst roads, I came back and found the same problem, so doubt if it's due to this, or might have the bolts been lose. . . About the FZ handlebar, YES SIR, will change it to FZ's as soon as possible. . . If it's a bend of either of the first two things you mentioned, axle or swingarm bend, how much is it going to put a hole in my pocket . . ?

Cheers!!!

Re: Honda Unicorn

Axle won't cost much, swingarm bend removal costs anywhere between 100-500 bucks, and also check your swingarm bushes too if they're worn out.

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Re: Honda Unicorn

Pweeh that's a sigh of relief. . . Anyways will be leaving it in another week or so, along with that will change the handlebars and then go to take on the curves. . .

Wait, you said bushes. . ? I have heard about this from one mechanic, he said it would cost around 600-700 to get it done properly. . .

Cheers!!!

Re: Honda Unicorn

Yea bushes will cost around 500

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Re: Honda Unicorn

It can be either worn bushes
Also yours is spoke model so get rim checked for trueness
There is a beading inside tyres, if it wears out the tyre wobbles rythmically
Lastly air pressures also play role in making rear end wobble

Hope it helps

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Re: hi friends waiting for a reply

Change the oil, mak isn't a good oil, you can use synthetic oil if you want but it won't make much of a difference on a uni, so you can try motul 3000 mineral oil 10w30 or try semi synthetic motul 5100 10w30, you can also try shell ax7 10w40. When do you change oil, after how many km?

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Re: hi friends waiting for a reply

Oil was changed on every service. about every 500 to 700km.

Even with castrol power1 engine ran ok for many km but suddenly one day on normal speed engine got stuck. next day service guy came and forcefully started engine.
checked oil and said oil ok but use 10w30 always. so I changed to MAK 4t plus from castrol power1. after few days the engine lost punch.