BritBike Forum logo
BritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike Sponsor SteadfastCyclesBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorHepolite PistonsBritBike Sponsor
Upgrade to: Premium Membership | Gold Membership | Life Membership | Vendor Membership | Site Sponsor Membership
Member Spotlight
Servodyne
Servodyne
England
Posts: 105
Joined: August 2013
ShoutChat Box
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
a word from..
Manuals on DVD (Shipping included)
Previous Thread
Next Thread
Print Thread
Rate Thread
Base studs and thread
#802327 03/22/20 5:36 pm
Joined: Sep 2009
Posts: 5
Britbike forum member
OP Offline
Britbike forum member
Joined: Sep 2009
Posts: 5
Hi all,

I have a few issues on my '67 Triumph Trophy 650cc. Just doing a top end refresh to stem an oil leak.

I was confused that 2 base studs are a different part number and have a dowel - whats the point of those two different studs and the dowel?

Second issue - one of those studs (the rear) the thread has gone, pulled out when I removed the stud - what's the course thread size, as I need to repair with a thread insert?

Thanks - Paul.

Support Your #1 BritBike Forum!

Check out British motorcycles for sale: British Motorcycles on e-Bay UK, British motorcycles on e-Bay North America
Re: Base studs and thread
biker_smith #802335 03/22/20 6:52 pm
Joined: Aug 2018
Posts: 76
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2018
Posts: 76
I have a 68 engine in bits - this was the start of the UNF changes so I am not absolutely certain that they are totally the same as 67. The threads into my casing are 3/8" BSW.
I gather you didn't mean the dowel is part # E1532 on the timing side front - the oil feed to the tappets.
With regard the studs, my barrel have two sleeves E1534A (labelled as hollow dowels so this is maybe what you are referring to) on the inner inlet side. These have slightly larger diameter studs to go with them ( E1534) than on the other 6 studs (E672). I make the studs about 4 thou larger diameter. With the larger studs and the sleeves, it positively locates the barrels in the casing. If they weren't there, the nominal 25 thou clearance in the barrel around the studs wouldn't assure the centralisation of the tappets over the cams.


68TR6P rebuilt as a C
70 TR6R
Re: Base studs and thread
Morrisey #802339 03/22/20 7:24 pm
Joined: Aug 2018
Posts: 76
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2018
Posts: 76
Sorry Paul - I gave the wrong part number for the fatter studs. They are E3523. I need to wear my reading glasses more.
Chris


68TR6P rebuilt as a C
70 TR6R
Re: Base studs and thread
biker_smith #802348 03/22/20 8:10 pm
Joined: Jan 2017
Posts: 1,234
Likes: 17
Britbike forum member
Offline
Britbike forum member
Joined: Jan 2017
Posts: 1,234
Likes: 17
Hi Paul, I have limited experience with the '67 motor, but some. Take this for what it's worth.

I believe the difference in the studs is the length of the lower thread making the center unthreaded part longer. Studs are lightly bottomed in the threads during install. I use Loctite 243 (eBay) or 242 (easy to get) to keep oil from wicking up the open threads in the center 4 studs & leaking out the top.

The 2) studs at dowels # E3523 (70-3523) have the shorter thread at bottom & wider center.

The 4) other studs are # E672 (70-0672).

As was stated the 2 dowel sleeves locate # E1534A locate cyl in relation to crank shaft so bores stay parallel to crank. That's important in my mind. So we want to save the diameter of the hole for the hollow dowels.

As you can see the lower threads are coarse, upper are fine. It is my understanding these are British Standard Whitworth 3/8-16 with 55deg thread angle.

There is a imperial National Coarse 3/8-16 with 60deg thread. Some say this size bolt will interchange with Whitworth. That I don't know. I've only used the factory bolts.

Helicoil kits are available in Whitworth 3/8-16 on both sides of pond. Helicoil type insert uses less diameter & tend to hold better than timesert or other sleeve type repairs. More importantly you may be able to preserve the bore for the hollow dowel.

I don't have a hollow dowel on hand to measure its OD. I cannot find spec on the minor diameter of the tap for insert. My hope is there will be original metal left in bore around the dowel so it can locate if even only on the tips of threads.

I've installed thousands of Helicoils. I have a few tips. If possible try to strip out all the old threads before drilling for taping. This makes drill follow hole better. Use a stack of washer as needed & nut on top, screw stud in a few threads, tighten nut & break out threads a few at a time.

Very important to drill hole perpendicular to case. By yourself side to side is easy to align, but front/back often user drills crooked. So have a spotter to look & have you hold drill perpendicular. Same with starting the tap. Keep it straight as possible.

A lot of chips will be generated. Best practice is to separate crank case & clean. If needed you might be able to stuff rags in case below hole & put tape across mouth. Use your best judgment on that.

If you are not practiced with Helicoil repairs you should practice on some scrap alloy. Go to auto repair shop & ask for junk water pump or the like. Drill holes & practice. We have one shot at getting this right & don't want to mess it up.

Don


1973 Tiger 750
Re: Base studs and thread
biker_smith #802364 03/22/20 9:47 pm
Joined: Aug 2018
Posts: 76
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2018
Posts: 76
Do
The 68 parts book lists the studs as having all the same overall length 1 5/8". On my cases, all the studs are screwed in to be the same height and the threads appear to have bottomed. The upper threaded portion on all studs are the same length so I am of the belief that the only difference is the slightly fatter midsection.
One of my barrels is missing the sleeves and the diameter of the hole seems to be 0.402", measured with digital verniers. The ID of the sleeves seems to be 0.378". The diameter of the sleeve studs is 9.49mm - (I only have metric mikes but translates to 0.374". The other studs were a bit thinner but need to clean up burrs first


68TR6P rebuilt as a C
70 TR6R
Re: Base studs and thread
biker_smith #802365 03/22/20 9:51 pm
Joined: Jan 2017
Posts: 1,234
Likes: 17
Britbike forum member
Offline
Britbike forum member
Joined: Jan 2017
Posts: 1,234
Likes: 17
This brings brings up a good point. If you are going to work on old Triumphs you pretty much a thread pitch gauge for all the threads on bike. For years I winged it. That was foolish! I finely got smart and got gauges for all. Made my life much easier. Every one needs at least 6” vernier calipers also.
In this case a screw pitch gauge & calipers would tell exactly what the thread is.
Also allows owner to verify threads on replacement parts.
Don


1973 Tiger 750
Re: Base studs and thread
TR7RVMan #802387 03/22/20 11:25 pm
Joined: Sep 2001
Posts: 1,218
Likes: 9
Britbike forum member
Offline
Britbike forum member
Joined: Sep 2001
Posts: 1,218
Likes: 9
Originally Posted by TR7RVMan
Hi Paul, I
Helicoil kits are available in Whitworth 3/8-16 on both sides of pond. Helicoil type insert uses less diameter & tend to hold better than timesert or other sleeve type repairs. Don

For some applications I prefer timeserts because they don't flex or move. For any thread repair where the bolt/stud is frequently removed and installed as a part of normal service or adjustment then timeserts are much more dependable. Spark plug holes are a prime example, Rocker inspection cap bolt threads are another. This difference is because one is a tightly wound 'spring', and the other a solid sleeve.

For Pauls application a Helicoil is OK because you repair then install the stud, Loctite it in, and never take it out again. So the helicoil never gets a chance to flex or move.

Re: Base studs and thread
biker_smith #802429 03/23/20 5:54 am
Joined: Jan 2004
Posts: 4,606
Likes: 16
Britbike forum member
Offline
Britbike forum member
Joined: Jan 2004
Posts: 4,606
Likes: 16
60 degree thread bolts will not interchange with Whitworth or BSF which are 55 degree. If you really do not want to mess it up, put the case in a mill vice and drill it there. The top of the stud does not have to be far off for the cylinder not to go on. Of course, in that case you could use a hand file and oblong the holes until it fits.
A spotting drill or screw machine drill should be used to clear out the threads for the insert. They are much shorter and stiffer than normal drills so will not be pushed off centre as easy.

Re: Base studs and thread
biker_smith #802434 03/23/20 6:46 am
Joined: Jan 2017
Posts: 1,234
Likes: 17
Britbike forum member
Offline
Britbike forum member
Joined: Jan 2017
Posts: 1,234
Likes: 17
Hi DMadigan, Thanks for pointing that out. Very true!! Tapping off the spindle assures straight threads as well.

I feel if at all possible keeping the diameter of hole such the dowel is in it's original location is most important.

If needed the bore will have to be trued & stepped dowel made. I don't know how far off the dowel could be before it causes problems. I've not ran into stripped hole here before.

If nothing else you could put both dowels in now, set on cyl & scribe a line around cly base flange. At least you'd have a witness mark if things went wrong.
Don


1973 Tiger 750
Re: Base studs and thread
biker_smith #802583 03/24/20 7:28 am
Joined: Aug 2018
Posts: 76
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2018
Posts: 76
My 1970 parts manual shows there are no sleeves, the studs are all the same part number, UNC/ UNF and 1/8" longer than the older ones. This extra lengh would be to accommodate the 12 sided nuts.
Be interesting to know the engineering reason why they did away with the sleeves, though the real driver was probably reduced costs. Was barrel location no longer necessary? Or was it all done by the oil dowel and they had problems fitting some barrels on if the drilling jiigs didn't precisely locate the component holes?.
For the bike rebuilder, are those sleeves really necessary even if there is no oil dowel?


68TR6P rebuilt as a C
70 TR6R
Re: Base studs and thread
biker_smith #802585 03/24/20 8:25 am
Joined: Sep 2009
Posts: 5
Britbike forum member
OP Offline
Britbike forum member
Joined: Sep 2009
Posts: 5
All - thanks for all the information. Regards - Paul.

Re: Base studs and thread
biker_smith #802656 03/24/20 7:07 pm
Joined: Jan 2017
Posts: 1,234
Likes: 17
Britbike forum member
Offline
Britbike forum member
Joined: Jan 2017
Posts: 1,234
Likes: 17
Hi All, My '70 parts book shows sleeves, part #13 on page with crank case. Even my '73 Tiger has sleeves.

The '69 Bonnie has sleeves. I personally removed the 4 center studs to Loctite them. However I didn't pay attention or photo the differences. I did one at a time. The base studs on '69 are different in thread. I don't know about other difference compared to '67.

Regarding the dowel for oil feed, it is not a locating dowel for cyl. It only aligns gasket to oil way.

I've found some base hollow dowels fit tight while other motors it is slip fit without need to push hard or drive.

Again it is my feeling that pistons going straight up/down in bores is important. Make no mistake Triumphs are not forgiving (just like all motors). Do things wrong & it will not work properly. Some guys get away with things by dumb luck. Don't count on it though. Almost every time it bites them in the rear.

Do this test. Put both dowels back in. Set cyl on without gasket. Wiggle around cyl & twist it. See the play. Mark the motor case. What do you find play is?

Sending to machine shop might be costly. Don't helicoil without practicing first.

But first things first. Did you verify what the thread is?

I still couldn't find minor diameter of Whitworth Helicoil tap. But I found tap drill is 25/64 (.3906"). Drills often do oversize so figure .395" Bore is .402" thanks to Morrisy. So that should leave some original metal to hold dowel in original position after threading. Double check my math!!

If you have a spotter for drilling & practice I feel you could do a good job at home. Again check my math I'm always subject to error.

Here's where I got tap drill size from.

https://www.eBay.com/itm/3-8-x-16-B...il-Damaged-Threads-14pc-Kit/143102493940

Again this is speculation until thread is verified.

Don


1973 Tiger 750
Re: Base studs and thread
biker_smith #802661 03/24/20 7:30 pm
Joined: Aug 2018
Posts: 76
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2018
Posts: 76
On checking again, you are correct TR7RV. I was comparing the parts list, not the drawing. I now see the 1970 book shows the hollow dowel has a different part (E8751) and listed as only one of them. So the barrels could still rotate a bit around the dowel to the limits of the outer stud holes..


68TR6P rebuilt as a C
70 TR6R

Moderated by  John Healy 

Link Copied to Clipboard
Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | DVD- Manuals & Parts books
Upgrade to: Premium Membership | Gold Membership | Life Membership | Vendor Membership | Site Sponsor Membership
Powered by UBB.threads™ PHP Forum Software 7.7.4