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120R Pushrod Tube help
#809340 05/18/20 6:58 pm
Joined: Jun 2007
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Got my ‘71 Bonny going pretty good. She starts on the first kick an pulls strong in all 4 gears. I look down and oil is seeping from the bottom of the front PRT. The rear tube is dry. I do remember having a heck of a time getting that front “wedding band” to go over everything, I tried every combination of the seals provided but none were even close. I had .060 clearance on the head as prescribed, before I bolted it down. Is there a secret to getting those seals on correctly?? Please enlighten me if there is....Thanks in advance!


If you love it, let it go. If it comes back, you've highsided!"
2016 Triumph Bonneville America LT
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Re: 120R Pushrod Tube help
DPO #809342 05/18/20 7:10 pm
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I think .060" is too much and use .030" to .040" on these. Any more and they'll distort or disintegrate. With the ring they don't have anywhere to expand.
I like the white seals, but the transparent ones are too soft and slippy I think.
Other than that there isn't much to it,

SR

Re: 120R Pushrod Tube help
Stein Roger #809352 05/18/20 7:57 pm
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2 members like this: Oil Changer, Stein Roger
Re: 120R Pushrod Tube help
DPO #809526 05/19/20 10:32 pm
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That’s a great visual! Thanks a million! I ran the bike at idle and 2000 RPM with MagnaFlux developer sprayed onto the area, no leaks noted. But if I ride the bike any distance, oil is streaming around the front part of the engine. Darn thing decided to start running on one cylinder so pushed her back in the garage and left for work.


If you love it, let it go. If it comes back, you've highsided!"
2016 Triumph Bonneville America LT
Re: 120R Pushrod Tube help
DPO #809557 05/20/20 5:46 am
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Hi DPO, The oil feed to rocker arms is quite low volume. The seals can seep bad, yet not stream out.

If... the oil runs out very bad & quickly especially heat soaked, I'd be 99.9% certain the oring on exhaust tappet block has cracked or deteriorated bad & finally fractured. I've seen this several times now. Even on my own bike. It can leak a cup per mile easily.

There are several things you can do with wedding bands. I like to put them on PRT first.

At the same time the bores in head must be deburred & smooth. The metal around outside of tappet block must be deburred & smooth. Inside of PRT bottom & outside of top must be burr free & not peeling chrome. Oil will leak behind the peeling chrome.

Only use viton orings on PRT. Verify they are viton material. Color doesn't matter. Viton can be made in many colors. The bottom white square seal is soft silicon

Crush can be anywhere from .030-.013" & will be good. I would recommend a smear of silicon on both top & bottom PRT orings. Black Suzuki bond works very well. Soft & not too thick to install. Cures in 24 hrs very strong. Be ready to go. Silicon orings, install quickly while still wet. Don't let it cure.

I recommend buying double orings. One set to trial fit & measure clearance. The 2nd virgin set for final assembly. Micro scratches on rings from trial assembly leads to leaks.

If head is skimmed crush may be too tight. Thicker head gasket or thinner square ring may be needed. That's a judgement call depending how far off you are.

I personally prefer to use feeler gauges between head & head gasket to measure as it takes the top ring crush into account to a degree. Just preference.

I always replace tappet block o-ring during repairs as they will most oddly leak after major repairs. Deburr & smooth the oring areas in cyl & on tappet block for these also. Never mess around with tappet block driver, never!!. Get one that replicates factory tool with the 2 prongs sticking out.
Don


1973 Tiger 750
Re: 120R Pushrod Tube help
DPO #809737 05/21/20 2:05 am
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Everything you ever wanted to know about push-rod tubes and seals.
http://vintagebikemagazine.com/technical-articles/push-rod-tubes/


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: 120R Pushrod Tube help
DPO #809782 05/21/20 10:34 am
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All good advice and things to look out for. One other suggestion is by Hughie Hancox in his book "Triumph, production testers tales" page 106. The inner 4 barrel studs are in through drilled threaded holes. Oil can migrate up the threads and appear as an oil leak coming from the push rod tubes when in fact nothing to do with an oil leak from tubes. Something else to look at and easy to fix with some thread sealer. Good luck, will follow your progress with interest.

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Re: 120R Pushrod Tube help
DPO #810123 05/24/20 4:25 pm
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Full days work got the head back off, checked, checked and triple checked front and rear PRT’s. Crush was either too much, or not enough from the kit from MAP. Finally got the crush that was best (about .020) and torqued it down. Rode bike about 7 miles and found oil streaming from rear PRT now! What a PITA! Towing the bike behind my motorhome up to Fort Mountain for a week on the 28th, AND A BAG OF RAGS!!!


If you love it, let it go. If it comes back, you've highsided!"
2016 Triumph Bonneville America LT
Re: 120R Pushrod Tube help
DPO #810132 05/24/20 5:22 pm
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Sounds like you've gone from too much crush, .060, to too little, .020. Too much will bend the head. Too little will not compress the seals enough to do their job. Have you checked the head for flat?
You have a 2016 and you still drag a 1971 around? Sounds like a love/ hate thing. Ha ha.


1968 T120R
1972 T120RV
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Re: 120R Pushrod Tube help
DPO #810671 Yesterday at 11:19 PM
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Often times the o-ring fitted on the tappet blocks get sheared off during installation

I like to use a sealer under the flange of the tappet block just in case the o-ring does not do its job

As others have stated, .060" is on the loose side and could be the culprit

What type of oil pressure do you have?


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Re: 120R Pushrod Tube help
DPO #810676 Yesterday at 11:53 PM
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I use sealer on the tappet blocks ,no o rings...... My T140 has only .020 crush. No leaks.....


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..

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