New pistons needed

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  • #9676
    SteveB
    Member

    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
    steveb

    #12599
    Anonymous
    Inactive

    Hello 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.

    #12600
    JohnS
    Member

    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

    #12601
    SteveB
    Member

    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 ?
    steve

    #12602
    Keith Goodman
    Participant

    Steve 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

    #12603
    Anonymous
    Inactive

    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.

    #12604
    DickH
    Member

    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 H

    #12605
    Keith Goodman
    Participant

    Steve, 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

    #12606
    Peter Hunt
    Participant

    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.

    #12607
    JohnS
    Member

    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

    #12608
    Keith Goodman
    Participant

    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

    #12609
    Peter Hunt
    Participant

    @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!

    #12654
    SteveB
    Member

    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

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