gtr 350 /175dt timing bar

[coxy]

gday all
if some one has a timing bar and nut for a 350 and a 175 could you please post a picture for me  please .cheers

[BS Mechanic]

Coxy,

Here's a picture:

[ziggy stardust]

BS mechanic, is that original or home made?

Z

[BS Mechanic]

That's from Richard, I believe it is a reproduction.  As I remember, the original pin was just a bit shorter, and had a more pronounced point on one end.

[deisher6]

There are different sizes.  I bought one from Richard for my GTO and it did not fit (he accepted it back).  A nail set, center punch, or drill bit work well as a substitute.
regards charlie

[ziggy stardust]

My toolkit is incomplete as there should be one with the GTR but I don't have one. I've used the shank of a drill but it would be nice to have the real thing.

Z

[BRT-GTR]

Ziggy,
         I am sure the tool kit item (68 bike) was probably just a 5mm diameter pin ( it was 42 years ago) with a taper on one end, as mentioned above, to match the crank dimples. I don't remember there being a drilled bolt with mine but there seems to have been a mod. Did early bikes have an 8mm tapped hole to take the drilled bolt above and later bikes just a 6mm tapped hole which will take a 5mm pin nicely. A minor cost saving measure I guess.
Hope this helps.  Regards, Brian

[coxy]

thanks thats the first time i have actually seen a complete one.it appears the same as mine less the nut are they the same for the 175 and 350 ,on my 175 if recolection serves me correct there is more of a cut away slot than i divit in the crank .cheers

[ziggy stardust]

In my GTR owner's manual it does show a bolt with a hole straight though and the pin, probably 8mm bolt and 6mm pin. I'd also heard these were correct for early models but my timing hole has a 6mm thread.

If I was to make one then I think a pin of 4mm may be too small, think I will make one just for the hell of it and try it.

Z

[BRT-GTR]

Hi All
       Lets cut to the chase. Hopefully a definitive answer which applies to the 350 and maybe the 175. These days i don't remember what I had for breakfast but I am astounded by how much I can remember from owning my original  GTR 42 years ago. I not going senile am I? DERRRRRRRR.

        I have checked my 350 engines, Early engine 918 has an 8 mm timing plug in the crankcase, the same size as the photo item above. The pin used in an 8mm timing pin adaptor really should not be be 6mm, because this would leave only 0.4mm of metal between the thread root and the hole for the pin ( 8mm tapping hole size 6.8mm). It would break the first time you put any spanner load on it. Bridgestone were better engineers than that. Judging from the photos, the pin is 5mm diameter which would  give a bit of strength to the adaptor thread.
        The later engine 6003 has a 6mm timing plug. I guess someone at Bridgestone ( ideas suggestion scheme?) realised that by drilling the hole to suit a 6mm plug they a)  save a small amount of time and money by downsizing the plug and b) they could do away with the need to supply an 8mm drilled adaptor for the pin because C) the internal diameter of a 6mm thread just happens to be 5mm so they could carry on supplying & using existing stocks of 5mm pins and it would it work just as well.

 If you make a timing pin, make it 5mm diameter, this should give a snug fit in a 6mm tapped hole , maybe test it first with a 5mm drill shank. A 4mm pin would wobble and may not give sufficiently accurate timing., although the pin facility is only really only a rough timing check. Accurate timing is better achieved using a dial test indicator down the spark plug hole. I seem to remember that the pin was between 25 and 30mm long , a  bit fiddly to use. 50mm might be better but dont put a lot of side force on it when in use, it could distort the alloy thread if someone was heavy handed.

On a similar theme, maybe someone can answer this one.(BS Mechanic?), Are the crankshaft components keyed or splined in any way to ensure that they could be reassembled in exactly the same radial position as they were when the crank was factory built. I did have a crank rebuilt once when it broke !!!! and I always wondered after that if the crank timing dimples or slots were in the right place relative to the big end pins.

Regards All,  Brian

[farmerdl]

If I remember correctly, and at this age it might not be correctly,  Don Vesco and later Tony Murphy spent a couple of seasons racing the GTR and I believe that, at least, at the crank center they would drill the components and pin them to make realignment easier and more accurate and to possibly provide a little less tendency to slip under racing conditions.

DL

[ziggy stardust]

Made this today for a 6mm timing bolt pin. More show than go as I would personally still use a 5mm drill shank.

I will most likely try it to see if there is any noticeable difference in the timing.

Z

[BS Mechanic]

Here's the most my memory can dredge up!
I don't think crank components are keyed in any way.  During manufacturing, and also at the crank repair press at Rockford, they depended on tooling which located the crank parts in the press.  Since each sequence in the crankshaft build process introduces a bit of clocking error potential, errors build up from the first flywheel with the timing indent to the left crank.  Using the pin method is generally good enough, but the most accurate way to time an engine is using a dial indicator to measure each cylinder's timing in inches (or mm) before TDC.

As a reference point, my engine #2390 came with the 8mm bolt and a 4mm pin.  If we can get a few more known serial numbers and timer sizes, maybe we can pinpoint closer when the factory changed.

[BRT-GTR]

BS
     Thanks for that. You've cleared up a mystery from 42 years ago. I often wondered how they could put the crankshaft back together, while maintaining the correct position for the timing indents. From what you say they couldn't.
 Taking a closer look at the original photos above, the adaptor pin (4mm) is half the diameter of the outside thread. Still think the pin on my original 350 (case drilled 6mm) was 5mm, seem to remember it didn't have much clearance and didn't wobble in use but I stand to be corrected. It was fiddly in use , dropping out at every opportunity if you didn't keep a finger tip on it. Z's 6mm adaptor arrangement looks much better to use. Nice job.

Brian.

[disc_valve]

Hi,

I agree with the comment about cranks not being keyed in any way. I've had 350, 175 and 90 cranks taken apart and all of them relied on an interference fit to hold things tight. I blew the centre main berings on my 350 years ago, and took it to a lical specialist to rebuild with new bearings (which I supplied). On return, the nechanic had scribed two faint lines across all four crankwheels befor stripping the crank, and used these as an alignment guide on reassembly.

It worked well. On the BS twins, you don't have to disturb the generator to split the cases and lift out the crank, so that was all in its original position. After rebuilding the motor I checked the ignition timimg with a dial guage without touching the points or generator, and it was still spot-on at the correct 3.33 mm on both pots. That, I think, confirms that the crank was rebuilt in correct alignment.

Graham

[ddog71]

I saw a timing bar on ebay approx 2 months ago but did not get a bid on it in time.! Haven't seen any since then. I guess it could be "Marine Corps" engineered. What size is the bolt and what is the diameter and length of the timing bar.?  Thanks... Tim