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DIY: Adjust Tappets on Hero Hunk/Xtreme
There have been numerous threads on tappet adjustment where discussions have overflowed to say the least. Nevertheless, it always helps when DIYs are available for specific motorcycles. Especially when the parts in question are tappets. Over the years I have observed that much has been written and advised on this enigmatic mechanical part and barring a few of fellow xbhpians, it has become even more confusing for the rest of the members. I hope that this thread will aid in quelling some doubts and kill myths that has grown around this important mechanical motorcycle part. This is my 1st attempt to formally create a DIY thread on properly adjusting tappets to get the best out of your ride. Positive criticisms are welcome and points to improve on DIYs will be much appreciated. 
Some common Questions and Answers
Q. What is a tappet?
A. There is actually no part called a tappet! It is a combination of some nuts, screw and mechanical parts that becomes a tappet in its own right. In simple words, it is part that 'recieves' linear motion more importanly than transmitting the same. As a result of its contact with the cam, it either imparts/recieves motion.
Q. What happens if the tappets are set 'tight' or 'loose'?
Scenario 1: Tappets are tight
As the clearance decreases to absolutely zero, chances of a bent pushrod/valve guide increases drastically. Moreover, it makes the valves open/close faster than the engine is designed to, leading to poor power output coupled with decreased fuel efficiency.
Scenario 2: Tappets are kept loose
Contrary to popular belief that tappets can be kept loose if one wants to extract maximum performance in terms of power and accelration is more a myth than a fact. Moreover, how much do our sub-250cc engines utilize this myth is a known fact to the ones who have tried and tested it. Honestly, I believe that more out of ego than giving a true feedback, many of us have argued that it helps the 'fast' riders. The loose rattling sewing machine like sound notwithstanding, it can be dangerous to operate with wider clearance, as can be known from the fact that A WWII fighter plane pilot caused his plane engine to catch fire! The reason? You guessed it correctly - loose tappets! Name? Alan Blumlein. Having said that, agreed that we are not riding aeroplanes, but still. Also, loose tappets make the valve close/open late leading to loss in power, and the cams & push rods have to work more to get the setup right.
It is important to complete all the adjustments when the engine is the coolest. I did it after an overnight gap of around 12 hours (includes sleep time! ) and started adjusting it early morning. As we all know that a clearances are less when the engine is hot and increases as the engine cools down. Hence it is imperative that the clearance adjustment be done on a cold engine only.
I will not bore you with more theory and get down straight to the DIY!
Tools required:
1. Phillips Head Screwdriver - to open the side panels.
2. Ring Spanner - 10mm
3. T-Handle with sockets - 10mm, 12mm
4. Feeler gauge - 0.12mm (for exahust side), 0.08mm (for inlet side) (I used a 0.10mm feeler gauge as I could not find a 0.12mm one. Hence it is very important to adjust the clearance even more perfectly.)
5. Tappet Adjustment Tool
6. Socket + Lever to rotate crank
7. Allen Keys - 10mm for crank inspection hole cap, 6mm for viewing hole cap
Step 1: Removing the Seat and the Tank
To gain hindrance free access to the engine head, you will have to remove the seat, the side panels and the fuel tank (in the same order). One has to be really careful while opening the fuel tank. As indicated in the pictures, there are four 'attachments' to the tank.
1. Fuel Level sensor cable - A cable that you'll have to unplug. The plug is visible close to where the tank is bolted on as soon as you lift the tank from the rear as indicated.
2. Fuel flow line and,
3. 2 breather tubes - one of them is a tank breather tube, and a little thinner one has 'tank side' tube printed on it.
Make sure that you do not use a jerking force to open the tubes - a slight twist at the mouth where they are attached beneath the tank is sufficient to take them out. After you have taken care of these tubes, you have to gently lift the tank vertically from the rear simultaneously as you slightly pull it towards the rear. Take care all the while while removing the tank so as not to damage the rubber mount grommets fixed on two sides of the frame towards the front. Keep your tank on a clean tyre/rubber mat/soft padded cloth. The hunk tank is massive thanks to its 'bullish' side panels and you wouldn't risk a scratch/damage to it! This will give you a clear access to the engine head. And all this while, keep the fuel tap 'off' - lest you want to bathe in a little bit petrol!
Step 2: Opening Engine Head Cover - taking out Air Feed tube
The engine head cover is bolted on by two diagonally placed bolts which should be opened by using a socket wrench/T-Handle to avoid damage to the bolts.These bolts have rubber mounts - take care not to lose any of them. Post unscrewing of the bolts, you will find that the compressed air tube hinders the removal of the head cover; so do away with the problem by opening the tube (rubber) which has a fabric weaving on it. Very carefully remove the head cover now so as not to disturb any collars/washers on the engin head. One of my collar (9mm) washers had got displaced and had fallen inside the engine head - all while trying to remove the head cover. Also the gasket should be kept on a clean surface away from any tools/sharp objects that might be lying around.
Refer to the pictures for a clear labelling and understanding the location/position of various washers/bolts/mounts underneath the engine head cover.
Step 3: Crank-Flywheel Rotation and Alignment
You can gain access to the flywheel by opening the 10mm window on the left side of the crank and the 6mm timing inspection hole cap to check for the 'T' mark that indicated the TDC - Top Dead Center position of the valves. This T mark is to be aligned with the index mark on the timing inspection hole. You will have to ensure complete closure of both the inlet and exhaust valves to adjust for accurate clearance. Do this by rotating the crank flywheel by using a socket plug until you find the T mark on the flywheel. Always rotate the flywheel in the anticlockwise direction. Make sure that the scribed lines on the cam sprocket are parallel to the cylinder head top surface with the 'O' mark facing towards the exhaust side.
Check for slight free freeplay on the exhaust and inlet valves by trying to pull (slightly only) them vertically upwards. This position is desired to start adjusting the tappets.
INTERESTING TRIVIA:
In my case, I did not have the 10mm Allen Key required to open the crank side flywheel inspection hole. So how did I rotate the flywheel? I got this wonderful tip from [MENTION=53807]paul.1911[/MENTION] - By putting the bike in top gear (5th gear) and slowly rotating the rear wheel anticlockwise and checking for the T mark on the flywheel! I was missing the 'F' and 'T' mark each time and so with the help of a flat head screwdriver inserted into the timing inspection hole, rotated the flywheel slightly to align the 'T' with the index mark! Now, one may find that the rear wheel doesn't rotate when put it top gear. Obviously, there is some compression to be overcome which is not possible by hand - in that case, simply remove the spark plug and you'll find the the wheel rotates freely even in top gear! Thanks to this guy, really!
Step 4: Correctly placing adjustment tools
Use a 10mm ring spanner and then place the tappet adjustment tool on top of the screw. Loosen the lock nut and taking care that the tappet screw itself does not rotate much. If tappets have no clearance, loosen the tappet screw slightly (very slightly) and slide the feeler gauge in between the space - remember you have to set a clearance of 0.08mm 0.12mm with the help of this metal strip.
Step 5: Adjusting clearance and Testing
Do the same for the exhaust side valve too. Again, fine tuning requires a par of deft fingers and the ability to 'feel' the movement. It will come from practice and experience. But desist from adjusting it everyday just for the sake of gaining experience!
The 'drag' should be felt here too - make sure that you do not have to forcibly push/pull the feeler strip - I will repeat - it should have just a 'slight' drag.
It goes without saying, how much 'fine' tuning is required for it to be near-perfectly adjusted. The feeler gauge should be smeared with a bit of engine oil to prevent damage to it and then slid in the gap. When you feel that there is slight 'drag' on the feeler, that is the time when the lock nut should be tightened. This is the point where most of us get it wrong. As you turn the lock nut, the tappet screw also rotates - even if you feel that it is not rotating, it does - microscopically! Therefore it is important that an opposing force by using the tappet adjustment tool is applied while tightening the lock nut. It took me a while to get it adjusted perfectly - sometimes it got completely tight/loose! By some hit and trial, I was able to adjust the clearance to my satisfaction.
The feel of the drag can be understood by the simple line figures (side view) that I have tried to indicate in the picture below:
Step 6: Learning to Hear the Sound of Engine
For the ones who had a tight tappet - Listen very closely as the engine idles and you will hear a very light 'chit'-'chit' or tick-tick sound. That is to make out that the gap has increased.
For the ones who had loose tappets - Instantly, you will no longer hear the sewing-machine like sound from your engine. It is pure bliss and the sound will turn a little bass-y.
Step 7: Riding your motorcycle and enjoying the ride!
Correctly adjusted tappets will help shoot up your mileage by 5-10kmpl as felt by many on this forum. I had tight tappets and post adjustment, I have straightaway gained 3-4kmpl at least. I am yet to check my mileage figures extensively but there sure has been some gain. Ride you motorcycle and enjoy the feel of it.
Again, it is important to learn to 'hear' your machine, feel it to diagnose and properly cure it of its problems. Rest, we all are here to help you out of your misery.
Tappets adjusted....Time to go for a ride!
Some common Questions and Answers
Q. What is a tappet?
A. There is actually no part called a tappet! It is a combination of some nuts, screw and mechanical parts that becomes a tappet in its own right. In simple words, it is part that 'recieves' linear motion more importanly than transmitting the same. As a result of its contact with the cam, it either imparts/recieves motion.
Q. What happens if the tappets are set 'tight' or 'loose'?
Scenario 1: Tappets are tight
As the clearance decreases to absolutely zero, chances of a bent pushrod/valve guide increases drastically. Moreover, it makes the valves open/close faster than the engine is designed to, leading to poor power output coupled with decreased fuel efficiency.
Scenario 2: Tappets are kept loose
Contrary to popular belief that tappets can be kept loose if one wants to extract maximum performance in terms of power and accelration is more a myth than a fact. Moreover, how much do our sub-250cc engines utilize this myth is a known fact to the ones who have tried and tested it. Honestly, I believe that more out of ego than giving a true feedback, many of us have argued that it helps the 'fast' riders. The loose rattling sewing machine like sound notwithstanding, it can be dangerous to operate with wider clearance, as can be known from the fact that A WWII fighter plane pilot caused his plane engine to catch fire! The reason? You guessed it correctly - loose tappets! Name? Alan Blumlein. Having said that, agreed that we are not riding aeroplanes, but still. Also, loose tappets make the valve close/open late leading to loss in power, and the cams & push rods have to work more to get the setup right.
It is important to complete all the adjustments when the engine is the coolest. I did it after an overnight gap of around 12 hours (includes sleep time! ) and started adjusting it early morning. As we all know that a clearances are less when the engine is hot and increases as the engine cools down. Hence it is imperative that the clearance adjustment be done on a cold engine only.
I will not bore you with more theory and get down straight to the DIY!
Tools required:
1. Phillips Head Screwdriver - to open the side panels.
2. Ring Spanner - 10mm
3. T-Handle with sockets - 10mm, 12mm
4. Feeler gauge - 0.12mm (for exahust side), 0.08mm (for inlet side) (I used a 0.10mm feeler gauge as I could not find a 0.12mm one. Hence it is very important to adjust the clearance even more perfectly.)
5. Tappet Adjustment Tool
6. Socket + Lever to rotate crank
7. Allen Keys - 10mm for crank inspection hole cap, 6mm for viewing hole cap
Step 1: Removing the Seat and the Tank
To gain hindrance free access to the engine head, you will have to remove the seat, the side panels and the fuel tank (in the same order). One has to be really careful while opening the fuel tank. As indicated in the pictures, there are four 'attachments' to the tank.
1. Fuel Level sensor cable - A cable that you'll have to unplug. The plug is visible close to where the tank is bolted on as soon as you lift the tank from the rear as indicated.
2. Fuel flow line and,
3. 2 breather tubes - one of them is a tank breather tube, and a little thinner one has 'tank side' tube printed on it.
Make sure that you do not use a jerking force to open the tubes - a slight twist at the mouth where they are attached beneath the tank is sufficient to take them out. After you have taken care of these tubes, you have to gently lift the tank vertically from the rear simultaneously as you slightly pull it towards the rear. Take care all the while while removing the tank so as not to damage the rubber mount grommets fixed on two sides of the frame towards the front. Keep your tank on a clean tyre/rubber mat/soft padded cloth. The hunk tank is massive thanks to its 'bullish' side panels and you wouldn't risk a scratch/damage to it! This will give you a clear access to the engine head. And all this while, keep the fuel tap 'off' - lest you want to bathe in a little bit petrol!
Step 2: Opening Engine Head Cover - taking out Air Feed tube
The engine head cover is bolted on by two diagonally placed bolts which should be opened by using a socket wrench/T-Handle to avoid damage to the bolts.These bolts have rubber mounts - take care not to lose any of them. Post unscrewing of the bolts, you will find that the compressed air tube hinders the removal of the head cover; so do away with the problem by opening the tube (rubber) which has a fabric weaving on it. Very carefully remove the head cover now so as not to disturb any collars/washers on the engin head. One of my collar (9mm) washers had got displaced and had fallen inside the engine head - all while trying to remove the head cover. Also the gasket should be kept on a clean surface away from any tools/sharp objects that might be lying around.
Refer to the pictures for a clear labelling and understanding the location/position of various washers/bolts/mounts underneath the engine head cover.
Step 3: Crank-Flywheel Rotation and Alignment
You can gain access to the flywheel by opening the 10mm window on the left side of the crank and the 6mm timing inspection hole cap to check for the 'T' mark that indicated the TDC - Top Dead Center position of the valves. This T mark is to be aligned with the index mark on the timing inspection hole. You will have to ensure complete closure of both the inlet and exhaust valves to adjust for accurate clearance. Do this by rotating the crank flywheel by using a socket plug until you find the T mark on the flywheel. Always rotate the flywheel in the anticlockwise direction. Make sure that the scribed lines on the cam sprocket are parallel to the cylinder head top surface with the 'O' mark facing towards the exhaust side.
Check for slight free freeplay on the exhaust and inlet valves by trying to pull (slightly only) them vertically upwards. This position is desired to start adjusting the tappets.
INTERESTING TRIVIA:
In my case, I did not have the 10mm Allen Key required to open the crank side flywheel inspection hole. So how did I rotate the flywheel? I got this wonderful tip from [MENTION=53807]paul.1911[/MENTION] - By putting the bike in top gear (5th gear) and slowly rotating the rear wheel anticlockwise and checking for the T mark on the flywheel! I was missing the 'F' and 'T' mark each time and so with the help of a flat head screwdriver inserted into the timing inspection hole, rotated the flywheel slightly to align the 'T' with the index mark! Now, one may find that the rear wheel doesn't rotate when put it top gear. Obviously, there is some compression to be overcome which is not possible by hand - in that case, simply remove the spark plug and you'll find the the wheel rotates freely even in top gear! Thanks to this guy, really!
Step 4: Correctly placing adjustment tools
Use a 10mm ring spanner and then place the tappet adjustment tool on top of the screw. Loosen the lock nut and taking care that the tappet screw itself does not rotate much. If tappets have no clearance, loosen the tappet screw slightly (very slightly) and slide the feeler gauge in between the space - remember you have to set a clearance of 0.08mm 0.12mm with the help of this metal strip.
Step 5: Adjusting clearance and Testing
Do the same for the exhaust side valve too. Again, fine tuning requires a par of deft fingers and the ability to 'feel' the movement. It will come from practice and experience. But desist from adjusting it everyday just for the sake of gaining experience!
The 'drag' should be felt here too - make sure that you do not have to forcibly push/pull the feeler strip - I will repeat - it should have just a 'slight' drag. It goes without saying, how much 'fine' tuning is required for it to be near-perfectly adjusted. The feeler gauge should be smeared with a bit of engine oil to prevent damage to it and then slid in the gap. When you feel that there is slight 'drag' on the feeler, that is the time when the lock nut should be tightened. This is the point where most of us get it wrong. As you turn the lock nut, the tappet screw also rotates - even if you feel that it is not rotating, it does - microscopically! Therefore it is important that an opposing force by using the tappet adjustment tool is applied while tightening the lock nut. It took me a while to get it adjusted perfectly - sometimes it got completely tight/loose! By some hit and trial, I was able to adjust the clearance to my satisfaction.
The feel of the drag can be understood by the simple line figures (side view) that I have tried to indicate in the picture below:
Step 6: Learning to Hear the Sound of Engine
For the ones who had a tight tappet - Listen very closely as the engine idles and you will hear a very light 'chit'-'chit' or tick-tick sound. That is to make out that the gap has increased.
For the ones who had loose tappets - Instantly, you will no longer hear the sewing-machine like sound from your engine. It is pure bliss and the sound will turn a little bass-y.
Step 7: Riding your motorcycle and enjoying the ride!
Correctly adjusted tappets will help shoot up your mileage by 5-10kmpl as felt by many on this forum. I had tight tappets and post adjustment, I have straightaway gained 3-4kmpl at least. I am yet to check my mileage figures extensively but there sure has been some gain. Ride you motorcycle and enjoy the feel of it.
Again, it is important to learn to 'hear' your machine, feel it to diagnose and properly cure it of its problems. Rest, we all are here to help you out of your misery.
Tappets adjusted....Time to go for a ride!
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