Never a Dull Moment

[Rusty's Uncle]

No little Fiat motoring yet this year as my 500 broke down on the 30th of last month. Got towed home and not touched the car until today. The breakdown was odd almost like running out of petrol. Anyway attempts to start resulted in a single fire on one cylinder then nothing. Engine would then turn once or twice then lock. I say lock because the only time I have had anything similar was when I had a blown headgasket on a 1.9 Tipo Turbo Deisel and the bore filled with water & caused a hydraulic lock. Not possible with the aircooled though  Had to have a think about this one and decided it had to be down to some sort of magor mechanical failure or a problem with the 123 electronic ignition & timing. I could turn the engine over OK by hand and there had been no loud noises at the breakdown so started with the timing and everything seemed to check out. Next I whipped off the rocker cover, all looked Ok but a quick touch of the rockers revead that those on no 2 cylinder had about a 1 centimetre tappet clearance  Thoughts of broken cam went through my mind then I saw that the nut holding down the rocker shaft post was loose. Started thinking I was loosing my touch as I had only recently had it all apart after my big overheat. Turned out the stud had stripped in the ally head , in fact the entire thread came out like a spring wrapped around the thread , I would guess also as a result of the exteme stress put on the engine by the overheating. So the old helicoil kit will be comming out soon to get it sorted but this was a new one on me 

[gsxr126]

Sorry to hear that Rusty. Shows we never stop living and learning. You're probably lucky it locked, i've experienced valve train failure with catastrophic results. Did you determine the cause of the post stripping the thread? Maybe find that out before the helicoil [-/

Oh............ and use thread locker on the post when installing

[smallcox]

Hi Rusty,

Had the same thing with my fiat a couple off years back now and as you said slowly lost more and more power with missfiring. thought I had a shagged head gasket at first but found one off the studs broken that hold the rocker shaft in place. Unlike you luck mate the head was ok

Not sure that the 8mm studs are upto the job( bit wimpy)

[Darrell]

  Happened to mine and I went to M10

A local expert tells me it must be happening because I've a hot head....

I left it at that as I didnt know which head he was referring to...

[Rusty's Uncle]

Minor progress today as I decided that I need to order some slightly longer helicoil inserts than the ones I have so that it gives the best result possible & I am a firm believer in the fact that a proprly fitted helicoil gives a stronger joint than the original especialy in aluminium. The fact that the entire thread from the head just "slid" out of the casting convinces me that it was all down to the massive stress of the overheating episode. Taken a picture to show the stud , coil of stripped thread & a repacement (too short) insert. The 18 ft/lbs torque setting for the rocker mount is not high & under normal conditions it should be sound.
Got the stripped hole tapped out now ready to take the new insert. Did it in situ no problem  [-/
So while I wait for my new thread inserts I am messing with Weber carbs so have got two 26 IMB & 4 28 IMB carbs stripped down on my table at the moment & it is all very interesting so will start a new carb thread maybe  

[Darrell]

Will you benefit from a longer insert given the amount of thread on the end of that stud seems not far-off the length of the insert?

[Rusty's Uncle]

The thread insert is about 4-5mms shorter than the stud thread so I want to do the best job possible. OK so I have to wait a couple of days but the inserts work out at less than 50p & I can play wiyth carbs in the meantime  [-/

[Darrell]

Carbs???

EIther a twin carb-ed monster will emerge from the Rusty camp or Mrs Rusty has thrown all out of the conservatory and a low carb diet with home gym installed in conservatory.

I suspect the collection has grown

[Rusty's Uncle]

Nothing too exotic I am afraid but may rank as tuning/modification for the 499ccs engine and of general interest to aircooled 126 owners  [-/

[Rusty's Uncle]

I ordered the thread inserts from "helicoilking" on eBay yesterday afternoon & they arrived in the morning post 
So fitted the rear stud , refitted the rocker shaft & got the torque wrench on the nuts. Front stud then pulled staight out same as the back one  even though I had tested it & it seemed very secure.
Next thread insert then fitted, reassembly and just to make sure they were sound I tightened them to 20 ft/lbs & no problems. Reconnected the other essentials and the little beast fired up to my relief  [-/

[Allan]

Me again uncle Rusty. I would have thought the thing would have been making a heck of a noise. I remember one being towed into my workshop clacking and rattling away because the owner setting his own tappet clearances, had read the .0059" clearance as 59 thou and set them to that.

[Rusty's Uncle]

Allan , good to see you back , I thought you might have been washed out on one of those land slips out to the East Cape 
I will be down around your way April time so looking to check out your 126.
As to the breakdown it was sudden , no noise  & no warning which was good in a way in that there was no chance of any major damage 
Yes manuals are fine for info & data  but a little common sense helps , like the guy replacing the head , nipped the nuts down in sequence then when the manual said finish with 55 foot pounds he kicked it 55 times 
Do not over do Waitangi Day  [-/