DR600 Compression Reading
Hi, can anyone advise on what should be a healthy compression reading on a DR600 ?
I feel that mines under powered and is using above an acceptable amount of engine oil, although there's very little sign that it's being chucked out through the exhaust when running, quite the opposite. Obviously, there are no big leaks that would otherwise explain it.
For a DR600, it's pretty easy to start especially when warm, not quite so when cold which would rather contradict matters.
The best compression reading I can get ( cold ) is 65'ish psi which my instinct says is too low for such an engine.
The speedo reading, which I tend to believe is true, is 47000 miles.
I have no previous service or repair history for the bike and I'm leaning towards the problem being that the engine is in need of a rebore, new piston and general top end overhaul but would like confirmation of how my compression reading relates to what is considered a good average.
Can't find any mention of it in the Factory Workshop Manuals that I have.


Firstly, you need to do a compression test with the engine hot otherwise you get a very low reading.
With 65psi I doubt the engine would run at all, so my gut feeling is that it`s wrong
The figure should be in the 120-150 psi range.
It`s very unlikely that you have a worn bore/rings at that mileage, and these engines are very robust
If you are using oil then maybe you are using the wrong oil as these were designed to use 10/40 mineral oil.
I`ve found more modern semi synthetic oils get used much more than older mineral spec.
I once tried fully synthetic and it burnt it off at a fearful rate.
btw the DR600 had the most criminally inefficient front brake known to man!
Right, thanks for that.
I'll recheck compression reading when hot and see what I get.
I have been using 10w-40 semi synthetic so I'll try mineral instead.
It's only that I noticed the oil consumption that set on the path to where I am, although I always thought that the performance should have been better ( max I can wind it up to is 65 -70 mph tops ) but I've nothing to compare it with and that might just be how they are ??
Basically not the "big thumper" I expected it to be but maybe thats me.
I know what you mean about the brakes but I've other older classics and they are even worse, I just ride according and not up the arse of other vehicles.
We've been spoilt by modern day advances on brakes.
Thanks again for your response, I'll let you know how I get on.

It should go a bit quicker than 65-70 though ragging it at 80 plus is not recommended.
Top speed was quoted at 101 mph back in the day, though I would have thought 90 would be about right.
Maybe someone has messed with the jetting or it`s a Swiss model with 27 bhp.
Definitely should be a lot faster than that . I have had mine re-bored and fitted a  Wiseco piston .Pulls 85 no problem. Would go a more but don't think it would be
right to cane a 37 year old. Even before re-bore would  pull 80 no problem. Mine use's quite a bit of oil so perhaps I should try mineral oil in stead of semi synthetic.
Also after re-bore I had a devil of a job stopping the clutch slipping. Tried new plates ,metal  and fiber, ,new springs ,different oils, nothing helped. In the end I put
an extra steel plate in clutch and that did the job. BigBob is right about the front brake. I rebuilt the caliper on mine. used a kit that replaced that weird OE  piston
with a stainless steel one and fitted a braided steel brake line. Made it a lot better. Still not going to do any stoppies but does slow the bike down better. When you
get it running right should be fun on twisty back roads. I've had mine 12 years and still enjoy it. Even embarrassed a few sport bike riders when they are being dopey.
Head light pretty poor as well so fit a LED bulb from classic car LED's. They have a choice of very good bulbs. Beam pattern very good so no issues with MOT. I have
also put one in the head light of my DR 800.


My bike
The front brake on my 600 was so useless that I ended up fitting a complete DR800 SR43 front end on mine, complete with Brembo disc and sintered pads.
Certainly stopped well after that. Why did they ever use a plastic piston?
I tried several LED kits on my Bigs, most of which didn`t last very long. 
These have proved to be excellent https://www.ebay.co.uk/itm/265836664293?...R8K37fvVYA
You should check out classic car leds . The one in my DR600 is 3 years old . Had no problems and ride with it on all the time and passes mot OK. Before I changed
bulb it was not safe to ride at night. If some one was behind me with retina burners all I could see was my shadow. The one I put in my 800 as a different style of
heat sink. Looks like regular bulb on the back just 8 mm longer. Bulb fitted OK but was a bit tight to get plug on. Not tried in dark yet but considerably brighter than


this is the one in my 800.
(16-08-2022, 07:53 PM)BigBob Wrote: It should go a bit quicker than 65-70 though ragging it at 80 plus is not recommended.
Top speed was quoted at 101 mph back in the day, though I would have thought 90 would be about right.
Maybe someone has messed with the jetting or it`s a Swiss model with 27 bhp.

It is a UK model from new.
I think I'll strip down the top end over winter and have a look, somethings not quite right and it's not a big job.
Will be more productive than watching shite on the TV !

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