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I thought as I was going to pull the head off Fish’s DR400 I may as well do a DIY to help others if they want to have a go
Fish’s bike wouldn’t start on the morning of day 5 of the recent 3 state ride. Not starting cold is a common theme with closed inlet valves. Recently Krusty’s DR did the same thing on the Nabiac museum ride he trailered his bike home to avoid the hassle of roll starting. Fish roll started his bike and did another 3 days and more than 1000kms after the failed cold start. Because the inlet valves don’t close thus sealing the combustion chamber the air / fuel mixture that should be compressed and then fired gets blown back up the inlet towards the carby. When you tow start the engine you wind it over at a faster pace then the starter motor helping build compression because of the extra speed this normally helps start the engine.
I had to go to Hornsby the other night so I picked up Fish’s bike and this arvo I removed the cylinder head
Here is a blow by blow
First the bike in question
Up on the lift stand
The seat was removed, two bolts at the back of the seat
Then the tank needs to come off, two bolts through the air vents for the front mounts
The rear of the tank is held on by the rubber strap
The fuel line in pulled on the tap, remember to turn the tap off
So the tank and seat removed give a cleaner work area
The coolant needs to be drained, I drained it here at the water pump inlet
Coolant drained
The other hoses need to be removed as well
Including the 90 degree neck at the front of the cylinder head, two 8mm headed bolts
Next the exhaust system complete needs to be removed
Inside bolt needs a long 6mm Allen key
The whole system needs to come off
Once off makes access easier
Now the front of the cylinder head is all clear
Top engine mount was next
The horn so the tappet cover bolts could be accessed and the tappet cover removed
The hose clamp from the carby to the cylinder head was loosened
The breather and oil return hoses on the top of the tappet cover were taken off
Then the tappet cover itself
I thought it best to double check it actually had closed valves. The engine needs to be setup on TDC (top dead centre) there is a mark in the left hand side crankcase
There is a mark / line on the flywheel see here in the timing hole, I wound the engine over in 5th gear via the rear wheel
To confirm all was right the marks / lines on the cam gears should line up with the head
Inlet cam
Exhaust cam
Cams and marks / lines
Now I checked the clearance between the buckets and the cams, the lobes of the cams can be seen with the inner base (lower part) of the lobes on the buckets
First the exhausts, the feeler gauge goes between the bucket and the cam lobe
.008 thou all good
When the inlets were checked I couldn’t get my smallest feeler gauge in that being .0015 thou, spec is around .004 from memory. FAIL!!!!
Head off
The cams need to be removed, this means the cam chain needs to be removed as well. The cylinder head bolts are under the cams on the cam chain side. Before you remove the cams and chain you need to release the tensioner for the cam chain. This one was fitted with an aftermarket manual adjuster. In the picture below you can see where the adjuster was removed from above the black hose
Cams and retainers
All the bolts loosened ready
Cam retainers / bosses removed
You need to not drop the chain down into the engine, so I use a cable tie to hold it up on the lower drive gear ready to go
Cams out chain held up
The two 10mm headed bolts on the timing chain side of the cylinder head need to be removed now see just to the right of my thumb in the below picture
Next the 4 main head bolts, the old manual decompression pin not used stops you getting a socket on it so it had to be removed. See in the picture below, bottom left side of the picture you can see the head bolt and the pin stopping the socket going on square
The pin needs to be removed, but of course the screw is a soft as a two stroke rider. I didn’t have an impact driver, so I used the below setup, turning the screw slowly while hitting the end of the screw driver, came straight out happy days
Finally there is a 10mm headed bolt that goes in and retains the pin, it goes in from the front of the head
The 4 main bolts can then are undone evenly, use a single hex socket you don’t want to round a bolt down in the head (6 sided socket)
The head is then removed from the mounting dowels be careful don’t go sticking screw drivers between the head and barrel because you will mark the sealing surfaces
Now the head is lifted off, first the cable tie is cut while I held the chain up. Once removed the chain is then tied up again
Inspection when the head is off
http://www.youtube.com/watch?v=WK9hRncjT7A
Later the head inspected when I get it to Nick at Teknik’s
cont.
That was a good DIY for us DRZ owners TB!
Krusty, you’ll be able to remove your head now in November after riding in the Cameron Corner dust full noise for a week !!
:laugh: :pinch:Nick
TB
Your probably correct there as mine were only at the lower end of in spec when I re shimmed
I guess I’ll keep up what i’ve been doing and it will probably out last me :laugh: :laugh:
Adam.
Awesome stuff TB… I look forward to the findings of the research… I’m pretty sure mine was dusted as the housing between the air filter box and carby was full of dirt, actually caked on the walls from the what the mechanic said…
From memory I think it was years 2002-2004 maybe to 2005 that supposedly had this deficiency..
Great stuff..
Nickj wrote:I know Boulder and fish run unifilters but I was wondering what others have in their Drz and if their is a link to dusting their ?I have 2 twin air filter which I rotate every ride. I had the valves checked at 9000km and all was good.
Nick
I run a unifilter as well. When I clean the filters, even after a dusty ride, the inner filter is as clean as the day it was first put in
I have yet to see any dirt on it Mine is a 2000 model so hopefully before the head problem being refered to :dry:
Good work TB I’m sure it will help many a nervous DRZ owner have the confidence to tackle a head job
I’m looking forward to the reassembly :ohmy:
PS how is the barrel for wear?
Adam
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