Technical question about the MTS 1200 engine
 

Hi all,

1) what is the compression (in psi or bar) expected to be ?

2) what is the minimum it is allowed to be ?

3) if one cylinder is down a bit with respect to the other, how different can they be (i.e. 1 bar different) before it is considered an issue ?

I know the compression ratio is stated as 11.5 to 1, but wondering what a compression check reading should give, and what would be considered acceptable / problematic.

As an example, if one were showing 165 psi is that good or bad ?
Presumably this sort of info is given is a service manual somewhere, but I've not managed to find it written down anywhere.

Cheers,
John.

Don't know the values associated with your engine, but when taking readings, all spark plugs out and hold throttle wide open whilst cranking.

If you are seeing 165psi that would be an acceptable reading and I don't like to see a difference of more than 5psi.

Hope that helps.

Thanks for the reply Ghost.

Yeah i know how to take the readings, and have already had my local independent do so.
I thought 165psi was acceptable, but wanted to know what they should actually be, and what the manual says.

My follow on question is, if one cylinder is significantly different, and all valve clearances are within limits, no fault codes given, no loss of water etc symptomatic of a head gasket, engine still runs pretty well, what is the likely cause ?

I think I know the answer, but looking for other opinions.

Ideally then you need to do a leakdown test, then you can determine if its valves or piston related, by air escaping at inlet/exhaust or through crankcase vent.

To explain, back in June whilst on a trip in France I had a major mechanical engine noise that at the time I thought was a broken cam follower (it was very top endy). I stopped, but was in the middle of nowhere, so we chose to limp the few miles to the nearest hotel. The bike still ran on both, but pinked if I tried to give it any throttle much above ~3k.
After stopping and then restarting the engine at the hotel, the noise was gone !
We rode the bike to the nearest dealer the following day (40km away), and they could find nothing. It generally rode ok, just hesitating occasionally. On getting back to the UK I took it to my supplying dealer for a check over and they again said there was nothing wrong, and said it could have been a bad plug ?!? so they changed them.
This despite me asking them to do a compression check (which I don't think they did, even though they changed the plugs).
Anyway, long story short, I took it to my local independent a week or so back to do a compression check as I was not satisfied all was well.
On cranking it over it was obvious one cylinder was spinning over easier than the other, and the bike is more vibey than it used to be, and I was not satisfied the noise I heard was caused by a bad plug, especially since it self-healed (never had a plug do that).

so the readings were 165psi front cylinder, 105psi rear cylinder :/

The supplying Dealer now has the bike, Ducati authorised the engine to be checked, its had its clearances checked / adjusted (Ducati told them to do these before a comp check - personally I would have done a comp check before as well), there are no broken followers, and now the dealer has done a compression check they have conceded something is wrong. The heads / barrels come off this week.

Just seen your reply, thanks for the further thoughts and I agree, that would have been my next step. Its in the hands of the dealers now though.

I can't explain the rattling noise that I thought was a follower, unless of course its eaten a ring...

Because i was unhappy they had not done as asked in July I requested to be called when the cam cover was removed so I could see for myself what state it was in. All looked ok.
Hopefully they will allow me to see the heads / barrels once they are removed too.

Time will tell just what it is,but in the mean time I'm trying to get the info the dealers are working to.
My big concern still remains that this would not have been found even at the service intervals unless I had done the comp check off my own back and pushed for them to follow it up.

60psi down is a major misfire, especially at idle. Good luck with it John all will be evident on stripping.

I have just been emailed the figures so posting them here so others know the answer.

Compression Ratio: 11.5±0.5:1

Engine cylinder compression measured with DDS instrument:
Standard value = 11 to 12 bar
Service Limit = 10 bar (MIN.), difference between the two cylinders = 2 bar (MAX.)

29psi difference seems to be a real wide tolerance to me, but what do I know...

So your good cylinder is in spec at 11.2 bar. I certainly would not accept 29 psi difference, as it would be impossible to get an even tickover. How they arrive at that level of difference is questionable.

I'd bee interested to see what the valve seats are like