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Old 18th November 2018, 11:38   #1
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Smile DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)

Hey guys,

At over 25k km's on the ODO, I'll be setting my tappet clearance for the first time on my Bajaj CT100B.

The process is simple, so here goes nothing;

1. Get the Seat off, followed by the tank.

You'd have to remove Allen-Key bolts on either side of the seat, followed by one holding the tank in place, I've posted several pictures of my CT100B naked in my Ownership Post for reference: Bajaj CT100B - Utilitarianism Redefined!

2. Remove the plastic window covers on the shifter side crank-case, they're easy to spot as they're the only 'BLACK' bits present;

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00079.jpg

You'd need a 17mm socket to remove the timing inspection cover.

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00078.jpg

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00077.jpg

You'd need a Coin and a pair of Pliers wrapped in cotton(To prevent scarring) to get the crank nut cover off.

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00076.jpg

3. Rotate the crank nut counter-clockwise using a 14mm socket.

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00069.jpg

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00070.jpg

4. While peeking into the timing inspection window while rotating the crank you'll spot the 'T' mark, which indicates TDC i.e Top Dead Center, the trick here is to note that you'd need to set it at TDC after compression stroke, so keep rotating the crank until you feel pressure, slow down once you do and keep going at a steady pace until you align the mark with the notch on the crank case as seen below;

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00075.jpg

5. Now you need to remove the tappet covers for which you'd need to use a 8mm socket.

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00086.jpg

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00083.jpg

6. Now using a 9mm Ring Spanner unlock the lock nut on either of the adjusters and with the help of the below special tool(Not necessary, can manage with a pair of nose pliers) adjust clearance with the help of a feeler gauge blade(The ASC uses a regular shaving blade, no pun intended!) as per recommendations mentioned in the workshop manual.

The tool in question, costs Rs.50/-, universal for most if not all motorcycles:

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00087.jpg

Feeler Blade in place, there has to be minimum friction felt while moving the blade around;

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00072.jpg

Since it was near impossible to source specifications from the local SVC I resorted to going with information available in a Scandinavian version of the CT100's workshop manual.

The clearances mentioned were Exhaust: 0.10mm and Intake: 0.7mm, now I knew the moment I saw it that the Intake clearance was way too high, even the little girl next door curiously peering into my garage felt that the clearance was too damn high, but keeping faith in the workshop manual I fired up the motor and as expected the motor made the familiar but disheartening sewing machine rhythm.

Comparison of both blades to give you an idea:

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00088.jpg

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00089.jpg

Stopped the motor and reset the Intake clearance to 0.07mm and all was well, guess they missed to print a '0', which I've edited and corrected in the spec sheet, see below;

Name:  CT100SPec.PNG
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7. Replace all 'O' Rings just to be safe;

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00080.jpg

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00081.jpg

Since the kit came with the timing chain inspection window 'O' Ring as well I decided to get it changed along with inspecting timing chain slack which was tighter than I'd expected for a machine that has been through as much abuse as my CT100B, Kudos Bajaj!

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00084.jpg

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-dsc00085.jpg

8. Now you'll have to put back everything in the reverse order you'd pull them out and then idle the motor for a bit to inspect if all went well, thumb rule states that it's better to go over than under as far as tappet clearances go, because if its over then it'll just rattle but if its under then you run the possibility of loosing compression when hot or even the piston hitting the valve, which would warrant a rebuild.

The plus side of DIY'ing is that you'd easily save yourself Rs.1200~1500/- which is usually the labor charge for setting tappet clearance at the ASC.

Cheers and Ride Safe,
A.P.

Last edited by ashwinprakas : 18th November 2018 at 12:07. Reason: Thread got posted by error when page reloaded, had to make necessary corrections!
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Old 19th November 2018, 11:06   #2
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Default DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)

Interesting DIY. Thanks for sharing. It's been a while since I maintained bikes so thistle was a good read. One thing - doesn't Bajaj specify hot and cold valve clearances? Or, is it assumed to be cold clearance? Also, how's your Zen doing?
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Old 19th November 2018, 11:19   #3
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Default Re: DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)

Hi! Good account of the job.

One thing I have seen is that many manufacturers of motorcycles state the valve clearances in the user manuals itself. Some motorcycles have same clearances for both inlet and exhaust valves, while for some, they may be different. Yours seem to be of the latter breed.

Did you set these clearances when hot or cold? Any indications that made you feel like they need adjustments? And last question, do you now feel any improvement/ changes in engine performance after the job?

Thanks for sharing this stuff.

Regards,
Saket

Last edited by saket77 : 19th November 2018 at 11:20.
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Old 19th November 2018, 22:24   #4
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Default Re: DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)

Quote:
Originally Posted by R2D2 View Post
Interesting DIY. Thanks for sharing. It's been a while since I maintained bikes so thistle was a good read. One thing - doesn't Bajaj specify hot and cold valve clearances? Or, is it assumed to be cold clearance? Also, how's your Zen doing?
Thank you for reading.

Bajaj doesn't specify anything for that matter, forget clearances even some of the basic(oil quantity) information provided in the ownership manual is incorrect and since I go through the owners manual before operation had reached out to them via their Toll-Free number to confirm the same, though I have to say their support network is commendable as I had a technician call me up soon after with the required information.

Though for some reason I was not able to get that level of support as far as technical information goes i.e valve clearances, which has led me to believe that Bajaj strongly insists that their motorcycles be serviced at their ASC's.

For motorcycles I presume that we have to assume that the clearances need to be set when cold, reason being unlike the Zen's manual there seems to be no mention of specific Hot/Cold Clearances, same was the case with the ZMA.

The Zen is wonderful thanks to you and everyone else who helped me get things going, the distributor cap, rotor, HT cables and Coil have been replaced and the car is performing way better than it used to, which has led me to postpone the remaining services until I hit the 1L mark by when I also guess I'd simply go for a new set of injectors rather than clean the existing ones, currently she's a bit shy of the 70k mark.

Quote:
Originally Posted by saket77 View Post
Hi! Good account of the job.

Thanks for sharing this stuff.

Regards,
Saket
Thank you for the kind words.

Quote:
One thing I have seen is that many manufacturers of motorcycles state the valve clearances in the user manuals itself. Some motorcycles have same clearances for both inlet and exhaust valves, while for some, they may be different. Yours seem to be of the latter breed.
Yes that is correct as far as premium offerings go, if my memory serves me right the ZMA's manual from Hero Honda did have the information provided in the first couple of pages itself.

The clearance for the ZMA was also even at 0.10 Intake and Exhaust, for the CT100B the ASC sets it to 0.10 or Shaving blade thickness for both intake and exhaust valves, but since I have severe OCD as far as technical specifications go I kept digging until a fellow enthusiast directed me to the above shown workshop manual.

Since the motor is fairly simple some ASC's even set clearances with neither a feeler blade nor a regular blade, having asked around quite a bit for clearances I've got a lot of bizarre replies and some of them were quite surprised why I'd even consider using a feeler gauge on such a rudimentary engine(CT100 comes in 2 Engine options now).

But since my use is a tad different from what the motorcycle was originally intended for I hope to keep things as per the book as far as I can lest while cruising at highway speeds for extended periods something abruptly gives up, even worse if in the middle of overtaking.

Quote:
Did you set these clearances when hot or cold? Any indications that made you feel like they need adjustments? And last question, do you now feel any improvement/ changes in engine performance after the job?
Dead Cold, even when the clearance was off the first try, the motorcycle was only run for a few seconds to confirm the same before being shutdown to reset to correct clearances.

Roughly 10k km's ago, during the GQ run, on the Satara stretch I'd gunned her at WOT for a continuous stretch where we covered around 150 km's before halting for breakfast, when I took off my helmet the motorcycle was making the distinct sewing machine sound which went away and never returned after we'd returned from having breakfast, since then I'd been considering resetting the tappets, the delay was due to difficulty sourcing specifications.

Now we both know it would be stupid for me to claim there was actually a noticeable performance difference after setting valve clearances but I can bet my sweet banana fry's that there really is.

Other than the usual top end clatter going mute, the motorcycle seems to carry a bit more oomph through out the rev-range.

There's this thumb rule test of riding hard to see if there is any compression losses or if something goes for a toss, so while climbing uphill I gunned the throttle and she did an indicated 70kmph in 3rd gear with the least bit of hesitation, which was a fair surprise as usually she'd be screaming to hit 60kmph.

The exhaust note while descending aggressive declines in gear have also changed, rather than the usual arhythmic note with random pops, she now has a more prominent but steady rhythmic note.

Logic says that the changes are psychological but I don't know for certain.

Last edited by ashwinprakas : 19th November 2018 at 22:28.
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Old 20th November 2018, 19:29   #5
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Default Re: DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)

Does the CT100 require valve clearance reset at 25000 kms? A bit surpirsed as this kind of problems show up with a lot more kms on the odo. 0.7mm for intake is not correct for sure as you have mentioned. it might have been 0.07mm for intake and 0.1mm for exhaust. Try this setting and see if the noise goes away.
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Old 20th November 2018, 19:54   #6
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Default Re: DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)

Quote:
Originally Posted by nkrishnap View Post
Does the CT100 require valve clearance reset at 25000 kms? A bit surpirsed as this kind of problems show up with a lot more kms on the odo. 0.7mm for intake is not correct for sure as you have mentioned. it might have been 0.07mm for intake and 0.1mm for exhaust. Try this setting and see if the noise goes away.
As per the manual it should be Checked and Adjusted every 5000 km's after the first inspection at 500 km's, I would've ignored it as I'd done with the rest of my motorcycles but as the clatter was quite audible on one instance I thought it would be best to settle the doubt once and for all.

The clearance was reset to 0.10 and 0.07 soon after I'd confirmed that the workshop manual was wrong, the racket being the obvious indicator.

There is no noise as of now, even before there was no concerning noise per say at idle during usual runs, but that one instance when things got louder than usual got me concerned.

I'd even mentioned it in my post from February, as it was bothering me even though it only happened once and never reappeared for the past 10k km's.

Quote:
Originally Posted by ashwinprakas View Post
13 days, 14 states, 7600 km's.

Completed the Golden Quadrilateral circuit on my CT100B.

The motorcycle performed brilliantly and saying that would be an understatement as she was pinned at WOT for 99% of the time, oil change was done within 2000~2500 km's range. Castrol Power 1 20W50 made her more rev friendly where as Shell AX5 20W50 and Valvoline 4T Premium 20W50 made her a bit sluggish at times. She did 100kmph true speed as per the attached cyclocomputer while clocking 115+kmph on the speedometer. There was mild tappet noise when the motor was hot after riding for 150+km's at a stretch but vanished after a short break. Overall the experience was wonderful.
Plus better safe that sorry, especially since the motorcycle is mostly ridden at wide open throttle and seldom used as it was originally intended to.
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Old 21st November 2018, 14:49   #7
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Default Re: DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)

Nice DIY and thanks for sharing! I'm interested in the tool kit you used (the spanner set). Can you share where to procure one from and how much cost?

Thanks.
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Old 21st November 2018, 16:59   #8
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Default Re: DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)

Quote:
Originally Posted by ashwinprakas View Post
At over 25k km's on the ODO, I'll be setting my tappet clearance for the first time on my Bajaj CT100B.
Lovely thread. Very nostalgic for an old man like me. Not that I ever tuned a bike.

Some 30 odd years ago I learned to service my dad's Premier Padmini from my dad and cleaning the spark plugs and checking the tappet clearance was part of this learning.
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Old 21st November 2018, 19:33   #9
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Default Re: DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)

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Originally Posted by emkay.india View Post
Nice DIY and thanks for sharing! I'm interested in the tool kit you used (the spanner set). Can you share where to procure one from and how much cost?

Thanks.
Thank you for reading.

1/2 Inch 6 Point Sockets from 8~23mm, some from Taparia and some from Eastman.

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-img_20181121_184233.jpg

3' and 5' Extensions and Ratchet from Eastman.

DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)-img_20181121_184343.jpg

The tools you see were procured individually as per requirement from the time I became legal to ride my first motorcycle and even to this date I'm adding new pieces as per situational demands hence it would be hard to give you an estimate of the price.

Though as for brands, my go to's are 'Eastman' and 'Taparia' as they're economic and well worth the money spent, the earliest of my tools are from 2011 and still going strong, I'm yet to break or crack anything.

I would suggest you do the same i.e purchase as per requirement, as it is easier on the pocket as the price of sockets/ratchets/extensions etc. are standardized and hence would make no difference if purchased as a set or individually.

Plus 6 Point sets have been rare and still are to a good extent, and since I'm very particular about the type of socket I use, buying individually was really the only viable option even if money wasn't a constraint at the time as we didn't have online options then and all the stores stocked only 12 Point sets which I'm not that confident in using as the chances of rounding heads are pretty high.

But if you'd insist on buying as a set make sure to only invest in 6 Point 1/2 Inch drive sockets. I have a 1/4 Ratchet as well from Bosch I use it with a 1/4 to 1/2 adapter as tourqing sensitive bolts/nuts with the Eastman Ratchet seen in the picture is pretty challenging due to its size.

I do have a ratchet type torque wrench from 'King Tony' but since classic indigenous motorcycles do not come with shop manuals that contain torque specs so I'd go with touch and feel to be safe.

Quote:
Originally Posted by navin View Post
Lovely thread. Very nostalgic for an old man like me. Not that I ever tuned a bike.

Some 30 odd years ago I learned to service my dad's Premier Padmini from my dad and cleaning the spark plugs and checking the tappet clearance was part of this learning.
Thank you for the kind words which have struck an emotional chord in me.

Though a scientist my dad worked on everything he got his hands on be it his old scooter called 'Super' or the Kinetic Zoom, though not a mechanic by any means he always tried to get things done on his own, which might've rubbed off even though I was a toddler at the time.

Funny thing is I've never worked with him per say as he works abroad and mostly because he's stingy when it comes to sharing his tools.
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Old 21st November 2018, 19:50   #10
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Default Re: DIY: Setting the Tappet Clearance of a Motorcycle (Bajaj CT100B)

Thanks so much for your detailed reply. Much appreciated. So I'll go with your words and start purchasing things as I go along. For now I'll get a ratchet and perhaps 8/12 mm sockets to boot with.
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