Compression test done - not good- help

The engine is a 1600 AD twin port, stock carb and exhaust, electronic ignition, put that in first for background info.

From what I can understand it doesn't matter so much how high the numbers are but all cylinders should be within 25 % of each other. Number 4 was the highest, number 3 was within 25%, number 2 was 37% and number 1 a whopping 50% out.
The engine is coming out tomorrow, I know I will most probably have to change the rings so will change the barrels and pistons at the same time.
I will check the cylinder heads for cracks etc and if good will clean them up and reuse them.

Is there anything else I should specifically look at that may cause a compression test result like that above.

As I am changing the B & P's should I just go for 1641 as it is no more work (not sure I would notice a difference) and if I do, do I have to go for twin carbs.

 

before you do check your valve gaps

 

Should have said that I did the compression check after I had completed a service and checked timing and valves etc.

 

I have a 1641, If I was doing it again I would have either stayed 1600 or gone 1776. twin carbs defo make a difference in a bus. did you have all the plugs out when you did the test and a fully charged battery? What were the PSi readings? did you have misfiring issues?

 

Did you do a wet test too, squirt of oil into cylinders then compression test again. If figures rise then think rings if no or little change think valves.

 

What were your readings?

Psi figures

 

Just been out again to retry and have tried the above. Neighbours love me.

#4 -112
#3 - 84
#2 - 78
#1 - 64

All last week it was driving fine no problems up and down the a1 (40 miles each way) cruising 55 - 60, max 60 on down hill for short period. real pain to start from warm/hot (even with hot start relay) put that down to temperament.

I know the figures are out of the parameters. Have decided to stick to 1600 as the increase in size to 1641 is approx -+1% so not really worth it! I will buy the best I can afford for B+P's and refurb the carb. Yet again my plans for the camping year have taken a kicking.

So get some B+ P's - those in the know can you let me know good makes or those to avoid if any. I will check the heads for cracks (at this point may have to use blue peter double sticky back plaster to fix them) and reuse if ok.

Is there any thing I need to check that may be a concurrent cause or systematic problem. Do not really want to split the case at this point.

Thanks again

 

Anything below 100 is bad

 

It's tired. Maybe it's been over heated and heads are loose. Maybe anything. You could do worse than removing rockers and checking the torque on the head studs/nuts you can get at. If these are loose, re-torque just these and try your test again. You never know your luck. This is just for testing, I'm not saying then carry on as if nothing had happened, though you could risk it.

 

I would not bother with rings when you can currently get piston and barrel set for £75 posted !!!

It could be the heads, valves or as Zed says loose studs.

 

I am off out to have another look after my man breakfast I have not stripped any big or essential parts out of the engine before so I may be gone a while.

From what I have seen when I get the barrels and pistons the rings come with it.
I will check and clean the heads and also the valves.

Then obviously more questions. It would be very kind if you could all wait on here until I come back

 

Yep piston barrel and rings, pins and clips in a set. GSF have 33% off at moment with sale33 code. so complete set is £75 posted.

 

Pretty sure GSF ones are AA pistons.

 

I think people have said before that if you do change the barrels and pistons then its worth changing some of the bottom end bits too as they will be worn and it might not like it!

I don't know what's involved but I am sure Zed said something about this in the past.

 

big ends. Its about all you can do without splitting the case. Don't drop any bits in though

 

I've dropped all the parts in, none of them can get past the cam. lol
Big end shells about a tenner and an hour max, so crazy fool territory not to.

 

No need to be de coking pistons cleaning ring grooves and honing bores when they are that price for new

 

There you go!

 

Checked the cylinder heads and if any thing were torqued over tight.
Got them off and cleaned them up, had a second opinion for an inspection and all is ok with them. While they are off it is it worth getting them ported and polished, as has been suggested to me. If so how much should I expect to pay.
I am not wanting to break any records or anything as it is a stock engine but I have until Monday till the barrels and pistons turn up and then put everything back on and tested

 

Did you call Rob?