Topic: SOHC/4 engine wear, solutions?

[jason41987]

in my reading of the honda SOHC/4 motorcycles, i hear a lot about how much the cylinders wear on the SOHC/4, and that they wear the cylinders to an eliptical shape, and could even wear them off parallel

heard this was due to a weaker metal in the cylinders... and that overboring slightly will fix the problem.. but how long term of a solution is this? after overboring, wouldnt the problem just happen again?... why not sleeve the cylinders with a stronger modern to reduce wear and requiring only a swapping of the sleeves to restore the bore?

[dave500]

if its worn out and needs reboring go for it,any engine wears its bore oval in time.

[jason41987]

if you bore it out though... would it not just wear itself out again requiring you to bore again, and then again until you can no longer bore it anymore?

i was thinking when i do end up boring it a size larger, have it sleeved back to stock bore and then if/when the problem surfaces in the future i can remove the old sleeve and press in a new one... thats what im thinking... has anyone done this?

[jason41987]

i havent taken my engine apart yet.. but umm.. do these things already have sleeves? and boring out the cylinder one size is just machining the inside of the sleeve?

[wrenchmuch]

There were 4 over bore pistons available from Honda. .25, .5, .75, and 1 mm over stock bore. You can find these kits many places. CycleX has them for instance. You can go all the way to 65mm in the stock sleeves. 61mm is stock. 65 mm is 836cc. CycleX has a kit for 850. This is the absolute limit for the stock sleeves. After this bigger sleeves and upper case boring is required.

[lrutt]

A clean bore and proper air filter and oil changes, it's doubtful you'd wear it out again unless you're racing or ride 20k miles per year. You will be fighting oil leaks from the head again before you need to worry about the bores.

[ekpent]

Think I remember a point Hondaman made in a thread that a first overbore in the stock sleeves will hold up very well,maybe better than new as the sleeve has been thoroughly heat treated etc.

[754]

 Yes they have sleeves, changeable. Bores will always wear over time. If you can wear out a fresh bore in 4 years running airfilters and good parts, on a Honda 4, you are riding more than 95% of riders..
 The reason 1st over may work wel on a relatively new motor, is twofold. First the sleeve/cylinder may have"seasoned" and changed shape slightly. another possible reason is some boring procedures are a bit more accurate than others.. some production bikes, spend less time on boring/fitting as a cost measure. Most Hondas are pretty good from the factory..

[jason41987]

thats interesting... and makes a lot of sense about the sleeves being heat treated and hardened from being used, and they would be... the way it sounded before was like it was a recurring problem, but i mean if its sleeved, i guess the engine can technically last forever then if taken care of

any idea what it would cost to have this bored a size larger? and would i need oversized rings, or larger pistons?.. also, what do those usually cost? i'll be taking the engine apart sometime within the next couple weeks and probably tackle the engine rebuild first

[dave500]

you will need a piton and ring set of the overbore size,like say a .25 oversize,the bore is machined then honed to the next size to suit the pistons,lets say you had a rusty damaged bore,it might need to be bored even bigger to say .50 or .75 to clean it up properly,if you have a stock bore just worn out .25 is fine,your not going to be reboring these like two strokes need often!a rebore on these will last you as long as you keep this bike man!ive just used this set from david silvers.
http://www.davidsilverspares.co.uk/CB550K3/part_29037/
a freind of mine has a machine shop,he charged me 220 to rebore and precision hone,each bore was sized to its individual piston and lettered.

[andrewk]

Wear is always a recurring problem in any internal combustion engine.  Nothing you can do to stop that- engines always have and always will wear over time/use.

A proper rebuild will last a long while if care is taken to do it right.  My 750 has over 45 thousand miles on the original build, and most of the parts were still well within spec when I took it apart for a transmission issue.  It's all in how it's cared for, both when ridden and when stored.

[Lostboy Steve]

I had my stock pistons thermal barrier coated on the top and micro slick skirt coated. I also had my valves thermal barrier coated. Can't say what it will do for my aggressive street riding, but on race bikes it is said to make a huge difference.

[lone*X]

I am curious about the perception that these engines have a problem with the bores.  Where did you read or hear that?  Many SOHC4's  run very high mileage without significant engine problems.  Lots of bikes on here still have the original factory pistons and rings running in the original bores.   

[andrewk]

The perception is probably driven by HondaMan.  His thoughts on HOW the bores typically wear is probably being misinterpreted as "the bores wear unevenly"

I don't know of an engine that, when the bore is worn out, that it's still straight.  Too many forces at play for things to wear perfectly. 

[Stev-o]

i'll be taking the engine apart sometime within the next couple weeks and probably tackle the engine rebuild first

Does the engine need to be rebuilt?

Probably not.

[jason41987]

the perception just isnt from one person, but a series of topics ive read here and on other forums of people dicussing overboring the cylinders due to wear, made it seem like it was a more common issue than it really is.. but it does make a lot of sense that the sleeves would then be heat treated and hardened making a second reboring very, very far down the road.. so ill ask around some machine shops, try to find out what itll cost to have them bored out and made parallel... id have to try to find a US based source of pistons though

[jason41987]

question..if my pistons are still in relatively good shape, would oversize rings not suffice?

[lone*X]

Bottom line.  What condition is the engine in at this time?  Can you do a compression test?  What makes you think it needs to be bored if you haven't dissembled it yet?  Your bores may be perfectly OK, or only need honing to seat new rings.   

[bryanj]

Jason, No you can not just use oversize rings, if wear is excessive you need oversize piston kits and a rebore.

Having said that back in the late 70's i stripped a 750 that had done 120,000 miles and the bore was within spec as were the ring gaps

[754]

 Sleeves are not hardened, soft actually..

[dave500]

over size rings go onto over size pistons and the bore to suit only,trying to fit over size rings on the stock piston wont work at all,,theyll most likey break as you try to fit them into the too small bore,,youll have to file heaps of them to get the gap correct then the circumference will be distorted anyway,,bores and pistons/rings must be of the appropiate size as a set.

[dave500]

slant sixes even?radial engines?boxer engines?

[jason41987]

its mostly a hope for the best, prepare for the worst kind of scenario.. bike hasnt been ran in atleast a decade, quite possibly much longer and there had to be some reason it stopped being used.. it has about 10,000 miles on it though, so who knows... cant even be sure if the odometer worked up until it stopped being used... but it had to have been abandoned for some reason

what would the worst possible scenario be?... well the worst one would probably be poor compression.. i have no meters to test this with, but i dont notice any cracks in the case, heads look pristine... its possible the carburetors being so cruddy was the problem.. hard to say not sure the carbs got messed up before or after it was left

[754]

 dont be surprised if you dont open it up, get it running, and get a few years out of it.
 I think you are worrying needlessly..
 Re Reply #22;
 I have heard of a V with over 400, 000 Miles on it, saw another a few years back with over 400, 000 miles, was on its second motor.. (both of those US made) I dont think the pistons lay on the bores, they have a layer of oil..

[wrenchmuch]

I think you want to try and get it to run before taking it apart. Does it turn over? Start by soaking the cylinders with 50/50 ATF/acetone mix. This will help free up the rings. Make sure you have spark, Clean the carbs, oil and filter, and check tappet clearances. Before first start crank the motor with the plugs out till you see oil at the 1 and 4 tappet caps then install plugs and try to start it . Doing a compression check on an engine that's been sitting will likely give you low numbers. If it runs, get it on the road for 500 miles then check compression.
I used to take everything apart and all I had was a bunch of stuff in pieces that was good to begin with. Slowly putting them all back together now.