Topic: #3 cylinder write off - oil everywhere-'72-350F

[JimD]

About 6 years ago i did a rebuild/resto on this '72-350F and couldnt have got thru it without the help and advise i got at this forum. I have a new problem. #3 always did smoke a bit but after a few years I pulled the top end apart and changed out the rings...didn't help. In fact it's worse than ever and really making a mess out the end of the exhaust, fouling plug and killing power. The bike far too clean to junk it otherwise runs like a top and is mint condition. My 19yr old son is the principal driver, the 350 is his pride and joy... I'd prefer to pull this apart for both the value in the bike and what he'll take out of the experience - but I'd like to know where it may go.
Does anyone think I have a problem with rod or piston or something else. Am I looking at re-boar and sleeves with different sized rings? Should I toss these jugs or even the entire top end? Any suggestions/links/ hints/help?. thx

[dave500]

what are the valve guides like on that cylinder?

[JimD]

I'll have to take the thing apart to know for sure but I didnt amend any thing (other than re-seating new valves)on the rebuild. I may be able to dig up a phot of that stage but what are you thinking?

[JimD]

attached is the best i can do. I believe Irecall getting new valves.

[dave500]

you didnt snag a ring when reinstalling?

[JimD]

Perhaps but i'm going to take it apart and try look at the guides as you suggest. Ive been reading and it seems to me that if i'm twice unlucky on the same cyl the problem is in the block.   Do I replace all in a repair or just the one (all i expect?) and what supplier (link?) gasket kit(?)  I'll get a shop to do it because Im not so confident if i can as i require a press etc.   thx 

[Red Good]

Nearly the only things that can cause it to smoke/ burn oil are the valves and guides and a worn cylinder/ bad piston or a ring damaged or in upside down . Really not much else there . Check them all closely and ask as many questions as it takes. Good luck . 

[bryanj]

If the bore is bad you get a set of oversize piston kits with rings and rebore to suit

[JimD]

can anyone help with access to guides; anyone have a suggested link where i can obtain one for # 3 ?

[bryanj]

Have you tried dave Silver?

[rb550four]

I was wondering if you did a compression test on it to see if there is any compression in that cylinder at all?
Do you see any broken inner springs in the head in #3 ?
I would do that before taking the head off which would be the next move.
Once that is off you can check the condition of your valves, Check how it seats......
Look in the cylinders and see if there is any scoring or digs, check the condition of the top of the piston....
You are already into a new set of gaskets so don't be shy , next you remove the jugs inspect everything for unusual wear,scoring, hotspots from blow by...if you can find that you're on . don't spin the rings around like we always do , just inspect it carefully for damage and installation correctness. (Not upside down) Check wrist pin and piston for slop. Measure the bore for round all over the cylinder in question, look for slop on the rod , just wiggle  it sideways.
  This isn't that hard, you and your son can do it. Get the manual for your machine so you have the particulars, both of you read it, take your time,  don't rush it, this is a learning experience, Enjoy the time with each other it goes by so fast.
  Let's hear what you find, take plenty of pics please, and most of all have fun!

[JimD]

ok.. perfect, that was what i needed, thanks!     one clairification I can do this without removing the engine cant I ?  last time I had it out but it seems to me that's not necessary ...  is there sufficient clearance to u/s of cross bar to remove the  the jugs without engine coming out of the frame?

[fmctm1sw]

ok.. perfect, that was what i needed, thanks!     one clairification I can do this without removing the engine cant I ?  last time I had it out but it seems to me that's not necessary ...  is there sufficient clearance to u/s of cross bar to remove the  the jugs without engine coming out of the frame?

Yeah, the top end will come off with the engine in the bike.

[Jim]

We,ve taken the head off and inspected... also removed the jugs as all looks very good.  I took the head to the machine shop as I dont have anyting to remove the valves. The shop advises the guides (all are very good. The Valves seat perfectly (de-glased and reseated 4 years ago). We will replace all the oil seals but none are so bad (#3) that the problem is obvious. They reccomended we remove the jugs and bring them in too. So we did that and they inspected/measure the jugs and find no issue.
I have ordered new rings and the shop will de-glaze once again and install new seals.

Here's the only thing I found..... when we pulled off the head we had left the spark plugs in situ. The plug on #3 is not seating as deeply as the others. This plug is constantly seriously fouled. It sits in its position likey as much a 3/16" more shallow than the other plugs.   The machine shop will be re-threading and fixing this issue.  (I'll get my son to post a pic subsequent to this note)
Clearly the question for me now is  "Could poor combustion or non combustion resulting from the bad position of this plug have been the cause of all of this oil blow by trouble?" (im on my 3rd set of rings trying to fix this bugger)   Comment?

[JimD]

can you see the difference in depth between #4 and #3 plugs in these pics?

[FuZZie]

Look at the difference in the color #3 has so much less carbon can't be igniting all the time?

[JimD]

Yes,  so I  think you are saying the fuel is washing the cylinder and not combusting (?)   .... but would that mean oil goes past too?  I dont know enough about whats happening in the suck, push, bang, blow process to know if there is an opportunity for oil to run into the pipe in that situation.   comments?. 

[tino montreal]

Compression test would have provided some additional info....ever do one during the rebuilds?
Can anyone suggest a good tool/link. I want to walk the talk as I want to practice what I preach 

[krusty]

Something is seriously wrong with that plug. Is it the same as all the others? It looks as though it has a shorter reach. Check its number against the other plugs. If its the same as the rest then the carbon build up in the threads may be preventing it from screwing all the way in. 

[JimD]

yes. can't tell what it's from but is fixed now,   anyone think I've found the problem or is it likely this can be the root of the problem.

[FuZZie]

Yes,  so I  think you are saying the fuel is washing the cylinder and not combusting (?)   .... but would that mean oil goes past too?  I dont know enough about whats happening in the suck, push, bang, blow process to know if there is an opportunity for oil to run into the pipe in that situation.   comments?.

I'm not sure, really you should hang in for someone more knowledgeable but I'm thinking you were running pretty much on 3 cyl.  So you may have been seeing something like any gas and oil in #3 getting blown out the exhaust unburnt, mixes with the carbon in the pipes then you see black oil like liquid come out the pipe.
Also have you been noticing any oil loss when checking the dipstick?

[JimD]

#3 would often run cooler than the others but not always, certainly last to heat up anyway.    yes we went thru quite a bit of oil (relatively speaking) .   pretty messy and all over the rear rim and light spray on the lic plate and tail light etc.  generally messy lots of smoke especially on warm up.  no one would put up with it. 
 

[seanbarney41]

I'm thinkin' you found your problem

[FuZZie]

yes we went thru quite a bit of oil (relatively speaking)

Can you be more exact? Like if the rings don't get to expand enough, you could use a bit on #3 but needs a judgment call depending on how much oil was getting lost.

[JimD]

Seanbarney- is there a reference or technical comment somewhere that discusses this issue |(do you know?)
FuZZie...  "use a little" what on #3?