I own a Royal Enfield Classic 350. At idle, the engine starts to produce a TICK TICK sound. However it vanishes when the rpm rises and when riding the motorcycle. This question is a very frequently asked question in many of the popular firms and even in that of the Royal Enfield official forums. The official Service center personnel told that its the sound of Automatic De-Compression occurring inside the new UCE (since 2010) engine. (Yes, in the older CI model Royal Enfield Engines, the rider had to manually De-Compress the engine before Kick Starting or else it the kicker would back fire). And i thought decompression was only required at the starting of the Engine or just before the ignition would start and does not have to be done while the engine is running. What really worries me is that i have heard this sound in many other bikes when the piston hits the tappet. OR on other words this is the sound of the piston hitting the tappet or the valves.. Needless to say, improper timing and wrong timing causes the piston to ht the tappet. Due to improper maintenance and "Do it yourself modifications" many of my friends have produced the same sound and eventually had to consult a mechanic to fix the issue. I really don't think its the sound of auto decompression. Any thoughts??
Most probably the sound is from a loose TAPPET in the cylinder block, usually it goes away after a few thousand kilometres but if it still persists then you need to open up the header and tighten the tappets with the help of the mechanic.
Its not advisable to DIY.
And No this is not a very serious issue. My personal bike had the same issue from day 1 and after 35000kms it is still slightly noticeable.The good news is that it does not affect anything in the long run.(At least for the sub 500cc bikes)
For a RE bike the noise might be irritating since the revs are low and the appeal of the bike is the thumping sound.
Tick Tick Sound you here during Idling is from Auto De-compressor. This Auto Decomp starts functioning below 350RPM. If RPM is raised this sound should vanish (This is applicable for new UCE engines).
In these Engines you also here some time Tick Tick sound after running the bike for few kilometers / engine warms up. This is basically maybe coming from the timing gear backlash acting, also in the high temperature Engine oil loose its property of viscocity (If Engine Oil is old) or could be due to Hydraulic Tappet (in new UCE engine Hydraulic tappets are used to avoid the tappet settings, Hydraulic tappets automatically adjust the gap).
So if you have tick tick sound in the ideling and even if it doesn't vanish after RPM increase then check the Auto De-comp (it is on the Exhaust timing gear).
If the sound is after running few kilometers or engine solidly warmed up then pls check for the timing gear backlash, Oil and Hydraulic tappets.
Mine is Cast iron 1993 model Enfield Standard, I have one query, What I mean to say is even I have the same Tappet sound, but if we are not tightening the tappet fully it will affect the engine, so if the sound is coming means it doesn't mean like your engine have any issue, as I know, you should service from a good mechanics, and ask him how to effect this for engine rather than reducing sound