Topic: CI pistons not central in bore

[disco]

Hi PeWe,

Bike is going in this week to have rods straightened. Will also have the jugs & head modified by opening the oil drains to 12mm. Also will fit a breather to oil tank. I hope that doing all that will solve the smoke/oil problems.

This bike was a ‘frankenstein’ assembled from various parts. I don’t know history of the rods. They appear OK but pistons are definitely sitting to one side in bore. Pistons also have uneven wear top/bottom on opposing sides as previously described. I’m convinced the 3 rods are bent.

Crank can only go in one location?

I’ll report back when I get it back together & running.

[PeWe]

If I suspected stock rods to be bent, I should look for a complete good low mile crank with rods on eBay. If bent, something bad must have happened. What about bearings? Rod bolts....

[disco]

Bearings & rod bolts were new

[rotortiller]

Call me cautious but bending connecting rods attached to the crank could damage the soft plain bearings if loaded up during the adjustment procedure. It's quite a lever after all. Just doesn't smell right to me. however I do wish the best of success.

rt

[BobR]

What piston-to-bore clearance was used? It should be a max of 0.0010" with those pistons. It would be really hard to see them "shifted" to one side if this much clearance was used.

 Reading with interest. I guess the tolerances intrigued me. I would have to agree that .001 should be very difficult to see. Googled a comparison. It seems a crazy close tolerance... 10 pennies out of 10,000 or 10 pennies width out of 47ft. bob

 

[crazypj]

Personally I would remove rods from crank for checking and straightening if needed.
The top of piston is probably 1mm smaller than the lower skirt as it gets HOT when running and expands to fill the hole.
For all of the pistons to be that far out I would think the bores are not at 90 degrees to base of cylinder and may be at an angle, particularly if top of block has been 'skimmed' at some time then cylinders bored from top down (set up 'upside down')
I always use base of block as reference surface and often check 'thickness' to make sure top and bottom faces are parallel. Checking bores are in correct orientation is more involved and rarely shows enough deviation to worry about although a 'perfect' set up will give lower friction and is 'nice' for race motors (also have to check cases, main bearing bore, etc)

[enwri]

Rods can be straightened without loading the big end. Was more worried about distorting the little end. The long bar I used (about 500mm) had a few mm. up/down movement at the far end, when in the other end was in the little end, Like how a valve has slight clearance/movement in the guide.
After bending, there was no extra clearance in that rod than in any of the others. Had it through all of the rods at one point just to make sure everything was aligned. Is it possible the little end is heat treated to harden up the hole? the rod itself was way softer than I was expecting.
Tried to illustrate how the rod was held/chocked in the crank web during the process.

[disco]

Crazy, it’s not all pistons that are off. It’s 3 of the 4 (1, 2 & 4).

The other possibility is that the little end/wrist of the pistons has been machined a bit off ie not square?

Thanks Enwri, I will make sure chocks are used.

Bob, my piston clearance was 12 ten thousands. (Or 1.2 thou)

[754]

Straightening Harley rods you grab it below small end.....  I did that in a Whizzer motor as well.
 Think of grabbing it with tee  handle tool, and the big end slides over against the sides of the crank.
 Which is not the same as hanging a bar out of one side of small end and reefing on it.

 Some of you should try it with a junk rod, you will be surprised how easy it is to bend one.

The trick is to get a close fitting block with a groove that fits The rod beam well, then weld that to your bar.

[Swoop]

What piston-to-bore clearance was used? It should be a max of 0.0010" with those pistons. It would be really hard to see them "shifted" to one side if this much clearance was used.

 Reading with interest. I guess the tolerances intrigued me. I would have to agree that .001 should be very difficult to see. Googled a comparison. It seems a crazy close tolerance... 10 pennies out of 10,000 or 10 pennies width out of 47ft. bob

FYI....you have added an extra decimal point to your comparison.
.001 vs .0001

[disco]

Rods straightened! Perfect alignment now. Valve guide clearances are spot on. Piston clearance also perfect at 0.0012”. Oil gallery returns opened up slightly to compensate for the larger HD non-waisted cylinder studs.

Just have to get it all back together now. Which thanks to Franks weldless frame kit is a relatively painless job! I’ll soon know whether i have cured its nasty smoking habit!!

[Terry in Australia]

Well done Disco, best of luck!

[PeWe]

Franks frame kit is useful! I changed cam twice the last 5 days with a test run between.

Edit: I did not have a lake of oil when lifting the valve cover.  Maybe your oil orifices allow too much oil to flow? I have HD studs too.
Bike was also parked on side stand. No oil tsunami when lifting cover. It should get some overflow if I had lifted the cam holders wich I did not do.
A little bit oil flowed on cyl 1 side, a spoon. I plugged plug cavity with paper to not get oil there and into the cylinder.

[disco]

Finally got some wrenching time & am re-assembling this engine. I have new pistons installed in barrels, new head gasket and o-rings in place and the cylinder head is on and torqued to 18ft/lbs.

I'm wondering what the consensus is for a light smear of sealant with the rubber pucks? I've used Permatex No 2 'non-hardening' sealant in past (underneath the pucks) & had good results. I'm also thinking (as alternative) a light smear of Honda-bond might be work just as good?

Just have to get the valve train in, carbs on and then it's "fire in the hole"!

[PeWe]

Non hardening sealer under the pucks is the way. Not too much since cam holder will press it out and it will go under the holder. Not so it can reach oil orificies.

[PeWe]

You have re-torqued head after 24 hours? That is a must with fiber gaskets. MLS does not need if RCS base gasket is used. I did it anyway.

[Terry in Australia]

Yep, Honda put a smear of sealant under the pucks Disco, so you should too. Per is right, torque the head, leave it overnight, loosen off everything and torque it down again, and it won't leak. Cheers, Terry.

[disco]

Thanks Per, I'll be sure not to use too much. This isn't my first rodeo! I'm re-torquing tomorrow after 24 hrs.

Hi Terry, so what do you think is better? Honda-bond or Permatex No 2? I'm leaning toward the Permatex because I've had success with it previously.

I'll advise whether this cures the smoking issues.

[Terry in Australia]

I think either would be fine mate, I think I've used both over the years, plus Hylomar, Threebond 1104, etc. The only sealant I've had that gave me any trouble was Loctite, which liquified when hot oil hit it. I better be careful though, gasket sealant threads can be as nasty as oil threads, or tyre threads.........

[disco]

OK I'll stick with Permatex No 2 then. Hopefully will be able to report back by next week as to whether it's cured.

[PeWe]

Oil thread?!! I love them
Sealant thread is OK too! I’m sure people use what they have around.
I have used Hylomar blue several times. Last time the black brown Permatex since the Hylomar had dried.  I banned Hylomar as case sealer after the cases weeped oil with it. It can be  Honda CB750’s bad breather design. Not enough, especially with bigger bores and more inspired driving.

I liked the Hermetite Golden as case sealer and under the pucks in the 80’s when it was sold. It had a banned chemical so maybe therefore stopped. There are a newer version of it sold today, maybe loctite.

[BobR]

I think either would be fine mate, I think I've used both over the years, plus Hylomar, Threebond 1104, etc. The only sealant I've had that gave me any trouble was Loctite, which liquified when hot oil hit it. I better be careful though, gasket sealant threads can be as nasty as oil threads, or tyre threads.........

 I get a kick out of sealant threads. Been working automotive (auto trans) for 40 years- before good RTV's came along- or at least were widespread. These days 1/2 the car is RTV'd together. Many auto transmissions are designed with only RTV for pan and cover gaskets. If I want to be extra sure it seals I'll use Permatex Ultra grey or Ultra black. Bob

[PeWe]

I’m curious about Loctite 515 as case sealer for next time. All my covers are good with the gaskets only. I banned my self when I had used Honda bond under the valve cover. It took hours to scratch and clean the mistake off. Honda gasket work fine, torque around 5-8 Nm, not more needed for no leak. It can be a good idea to use time-serts in all threads. My K1 head has extra rotten alu.

[Terry in Australia]

What's happening Disco, you got that bike back together yet mate?