- This topic is empty.
-
Posts
-
Hello,
i have done a compression test on the RB today and they are all 140 psi. they should be 170 ish ,so I have decided the pistons need replacing.
I am not bothered about standard pistons ,so what should I use ? My first thought is CB1100F Wiseco 72mm pistons.
What other options are there ?
Any advice welcome. thanks
stevebHello Steve,
Why new pistons?
May be you only need a new set piston rings and a cilinderhead fresh up.
Take care with removing the cilinder bank.Good luck,
Wout.
Steve,
Myself, I wouldnt worry about it. The important thing is that all cylinders give the same reading. Variations of more than 10% between cylinders may indicate a problem.
Your slightly lower reading than expected could also be explained by not having the choke and throttle fully open while cranking.
My RD gives about 145 psi on all cylinders, still pulls like a freight train and always gives me an adrenalin rush.JohnS
I had the throttle fully open but not the choke !.I will pull it apart and investigate it before i buy any pistons. Wout I never even thought of new rings, I jusr assumed they were no longer available ?
steveSteve I am sure I read in an older thread about using CB1100F rings on a R piston, they are part number 13011 MG5 004 and are still available, seen them on ebay http://www.ebay.co.uk/itm/Honda-NOS-83-CB1100F-Piston-Ring-Set-1100-Super-Sport-13011-MG5-004-/320884802167
Wout will know if they fit
These are in the US but you may find elsewhere
Good luck with removing the Cylinder, they can be a pig to remove
Keith
The cb1100f piston rings fitts the R-piston without problems.
I have used them more than once the last years.
You also have to hone the cilinder sleeves when you are going for new piston rings.
And you have to measure everything to check the minimum values.
I have made a special tool to remove the cilinders.
Take care with the cooling fins, they got damaged very easy.Wout.
I must admit that I wouldn’t bother……140 is fine and it is often true that a looser engine goes rather better!!
And, with any major maintenance work there is always the spectre of something going wrong….
Especially with the well known 1100r problem of removing the barrels.
Another viewpoint to chew over…..!!
Dick HSteve, if you are going racing with this engine you will need to restore the compression, especially if you are going for big carbs as well, I dont know what the compression should be on a 1100R but a 1100F should be 170 psi +/- 28psi
Maybe a valve job will help to restore some compression especially if the engine has been run with tight valve clearances
Keith
Yes, mine has 170 in 3 cylinders and 130 in the 4th, so will soon be looking into that. Will start with valve clearance check, but I suspect it’s going to need more than that….oh well, just another job to do.
Peter
You can put just a tea spoon of oil into that 4th cylinder, then check the compression again after a few minutes. If it brings the reading up to the others then its a ring problem. If the reading is still low, the problem is in the valves, either seals or clearance as you suspect.
JohnS
I did a compression test on my R this morning
I bought this earlier this year and serviced it and set all the valve clearances to .005”, have down approx 1000 miles on it now
Bike start and runs well and does not smoke but sometimes does not fire straight away on cylinder #2
Results are as follows, figures in brackets are with oil added to cylinder
Number 1 160 psi (195 psi)
Number 2 120 psi (165 psi)
Number 3 115 psi (115 psi)
Number 4 160 psi (210 psi)
Number 1 & 4 show reasonable compression, number 2 points to rings and number 3 leaky valves
Looks like Engine out time
Keith
@JohnS 3418 wrote:
Peter
You can put just a tea spoon of oil into that 4th cylinder, then check the compression again after a few minutes. If it brings the reading up to the others then its a ring problem. If the reading is still low, the problem is in the valves, either seals or clearance as you suspect.
JohnS
Ok cheers John, no probs. It uses a little bit of oil and mates have noticed a bit of smoke on overrun (cos I’m always in front haha).
I’m hoping the investigation can start in the next few weeks, I haven’t been using it for a while until it’s sorted, and I want to ride it!I have just done commpression test again with a hot engine and full choke, the readings are 160/160/150/160 .
I put some oil in cylinder 3 and tried it again. Its still 150. Next job I will check shims ,although its hardly done any miles since I last did them,
I have decided against racing it now, it would cost too much to make it competitive against 150 bhp Katanas etc. So I will be using standard parts to keep it going.
steveb
- You must be logged in to reply to this topic.