Enfield UCE - Tappets and decompressors
Posted: Tue Aug 25, 2020 10:33 am
For those with unit construction Royal Enfields.
Although fitted with hydraulic tappets there are items on the timing side that do require attention.
Firstly the decompressor, it's an automatic type controlled by a bobweight and a hair spring. The springs really are very fine metal and can loose there 'spring' or the tiny activating pin can get sticky in its slot if crappy oil has been used. either way if your getting a distinctive clank at low revs (especially when starting from cold) and it disappears as the revs increase then it's the decompressor that needs cleaning and a new spring.
Secondly if your bike is noisy at idle....
Do you hear the clackity sound?
Thats the cam gears with too much backlash so they chatter between loading in each direction. Luckily on this model the cam spindles are fitted with eccentric shafts so they are adjustable. Sadly you will need to remove the tank and rocker covers because moving the gears out of mesh means the hydraulic tappet will drop down and you will need to slacken off the rocker blocks to get them back in.
Do the adjustment in the following manner - set the engine to TDC so all the cam timing dots align, disengage the inlet cam gear by pulling it forwards (the tappet will fall down) and then unlock and adjust the exhaust tappet so the backlash is only just removed between the exhaust cam gear and the crankshaft. Then do the inlet cam; again only just enough to remove the backlash between the inlet cam gear and the exhaust cam gear that drives it. There is no adjustment for the oil pump (plastic) drive gear.
Compare the sound after (yes I know the idle speed is lower)
As always when replacing the outer cover make sure the oil feed O-ring stays in place.
Stay chipper - it's only nuts and bolts
Although fitted with hydraulic tappets there are items on the timing side that do require attention.
Firstly the decompressor, it's an automatic type controlled by a bobweight and a hair spring. The springs really are very fine metal and can loose there 'spring' or the tiny activating pin can get sticky in its slot if crappy oil has been used. either way if your getting a distinctive clank at low revs (especially when starting from cold) and it disappears as the revs increase then it's the decompressor that needs cleaning and a new spring.
Secondly if your bike is noisy at idle....
Do you hear the clackity sound?
Thats the cam gears with too much backlash so they chatter between loading in each direction. Luckily on this model the cam spindles are fitted with eccentric shafts so they are adjustable. Sadly you will need to remove the tank and rocker covers because moving the gears out of mesh means the hydraulic tappet will drop down and you will need to slacken off the rocker blocks to get them back in.
Do the adjustment in the following manner - set the engine to TDC so all the cam timing dots align, disengage the inlet cam gear by pulling it forwards (the tappet will fall down) and then unlock and adjust the exhaust tappet so the backlash is only just removed between the exhaust cam gear and the crankshaft. Then do the inlet cam; again only just enough to remove the backlash between the inlet cam gear and the exhaust cam gear that drives it. There is no adjustment for the oil pump (plastic) drive gear.
Compare the sound after (yes I know the idle speed is lower)
As always when replacing the outer cover make sure the oil feed O-ring stays in place.
Stay chipper - it's only nuts and bolts