GTO help needed please...

[steve]

Having just spent several months doing some refurbishment work on my GTO, it was a real disappointment to take the bike for a short test ride only for disaster to strike  After about half a mile of riding I slowed for a junction and there was a split second of clattering noise from the engine. I stopped to turn the engine off and noticed that the kickstart lever had dropped from its normal position to approx 2 o'clock. I could still push the lever down but it wasn't engaging, although the spring would return it to the 2 o'clock position. I had no option other than to push the bike home.

After a couple of chats with Brian (BRT-GTR)...(thanks Brian!) and removing the RHS cover, it was obvious that kick start gear C has lost half its teeth...and while the adjacent gear B looks ok in the picture, the large driven gear is hiding the fact that this has 4no broken teeth! The small kick start gear A at the rear of the driven gear seems to have come out unscathed. It also became apparent why the kickstart lever had dropped...the little ratchet pole behind the kickstart pawl had come out of its hole and turned 90 deg and was trapped, thus holding the kickstart lever at the different angle. Whether this caused the problem or happened as a result of the gears breaking is a mystery to me.

My concern is why this has happened...I can replace the broken gears and put everything back together, but worried this could happen again, so I'm hoping that someone can point me in the right direction. Just to give you some background info..the refurb works didn't involve an engine rebuild as this was done 3 years ago and everything has since been fine. However, what I had done was to remove the left and right cases to repaint them. As I recall, I didn't disturb any of the kickstart gearing after removing the cover although once I had reassembled everything, I did notice on the odd occasion, that the kick start lever could be depressed without actually engaging. The next time it would engage and everything seemed ok...I should now have taken more notice of this!

Would be grateful for any ideas or thoughts...thanks, Steve

[moonpup]

Steve,

Wish I had an answer as to the "why" myself. About a year ago, I picked up a GTR that had been sitting because it had a "kick start" problem. Found the same gear issue once the right cover came off.

Would love to hear of a way to prevent this, as it apparently isn't a "freak" occurrence with the 350's.

[slawsonb]

I discovered this issue as well on a parts bike. The undercut design of this gear creates a weak link, so the failures probably stem from the gear dying and all the ancillary rearrangement of pawls and poles, etc is a result (my guess). Sorry to hear about this Steve, but at least you were only a 1/2 mile from home.
...bert

[BRT-GTR]

     Hi Steve,
                     '' Just looking for clues at the scene of the crime'' as Joe Walsh once sang.

       This is pure speculation based on what I can see in the photos. I've also had a play with the offending parts on the bench this afternoon.
     
 The most obvious cause for the damage would be a foreign object becoming meshed in the gears but where's the object ?  I think you can rule out Gear B failing first, it is only an idler and carries very little load , being used to spin the rev counter gear, through gear C,  when the engine is running.

  The gear teeth on the broken sections of Steve's kick gear C don't appear to indicate any notable damage, unless it's just not visible. This makes me wonder if the real villain here is the ratchet pawl which has somehow jammed and broken a  section of  the gear away. The broken section has then hit a tooth on gear B and sliced a section off. I assume the four short pieces we can see in Steve's second photo are the sliced off ends of the teeth from gear B. This may explain the brief clatter. It is also noticeable in Moonpups photos that the teeth on gear C may have been broken away in sections, 2 or 3 teeth at a time.
   
   On the face of it the ratchet pawl can't jam when the engine is running. As the kickstart returns to it's rest position the pawl is retracted by it's stopper plate and is held clear of the scallops on the inside of gear C. It runs with very little clearance between the end of the pawl and the inside of the gear.

  There is a right and a wrong way to install the ratchet pawl, it's detailed in Fig 37 of the manual (but not very clearly) and Figs 74 & 75 ( the drawings here in my Rockfords manual are wrongly transposed, the lower drawing is the kick position with the pawl extended and the upper is the cruise position ) .
      So I tried to see what would happen if the pawl was installed the wrong way round, with the acute corner facing outward to the ratchet scallops. First of all, its sits deeper into the scallop depressions on the gear and applies more of an outward force to the gear wheel/teeth rather than pushing the gear round. In fact it looks like the tip of a cold chisel, clue? It still does turn gear C and ratchets nicely when C is spun.
     However, when the kick starter returns to it's rest position, the stopper plate is not able to fully retract the pawl and it continues to ride over the peaks of the scallops on gear C. In fact it is forced onto those peaks.  It fouls because the acute angled side of the ratchet is longer than the other side , due to the slanted end, and is enough to take up the designed clearance. It will still ratchet,all the time the engine is running,  with gear C jumping up and down. This generates a noise but I am not sure you would hear it with the engine rebuilt and running. Moonpup's  photos appear to show slight flats worn on the peaks of the scallops, a reversed ratchet could produce these.

     I can't say for definite a reversed ratchet is the reason for the broken gears. I still can't see how the ratchet can jam and split the gear even with the ratchet reversed but it would certainly apply more of an outward force to the gear and teeth, which I think is what we see.  A kickback from the engine would certainly put a lot of stress on the ratchet and gear when starting the engine but I don't remember them having a tendency to kick back. Also, after a missed kick, a quick jab on the lever to bring the ratchet back up would also stress the gear.  BS clearly thought the correct ratchet orientation was  important enough to highlight it in the manual but you have to look very closely to see that the end of the ratchet is not machined square and it is easily replaced the wrong way round.

     I can't really think of anything else that could split this gear. It is only stressed when kicking up the engine, the rest of the time it just drives the rev counter worm gear. So maybe it will work for a while with a reversed ratchet pawl  but eventually cracks the gear with the consequences shown in the photos. I'm open to other theories. Another one of those BS mysteries like the cracked clutch plates.
     As a matter of interest the kickstart ratchet pawl is identical to the two used on the gear change drum, they are interchangeable with the same part numbers.

   Brian,       

[moonpup]

Brian, I originally thought you may had been on to something with the "reversed pawl" theory as I didn't pay any attention to the backside of the gear, so I went back out and took another look. Obvious flat spots at the peak of every scallop.

Then I remembered I had a nos gear and after checking it out, I saw that the flat area is original to the piece.

The "reversed pawl" may still be the culprit, but it didn't cause the flat spots.

[slawsonb]

Life's been good to me so far! Yeah, yeah, yeah!
(Couldn't resist...Joe Walsh fan...)
...bert

[BRT-GTR]

          You're right Moonpup, just had a better look at one of mine. It does have small flats but not quite so pronounced and obvious as on yours. Any sign of rubbing or scuffing on those flats. Great photo and lighting, by the way, shows exactly what you referred to.
          Yep, me too, Bert.      Brian.

[moonpup]

Here's a close-up of my broken gear and to be honest, it doesn't look very worn at all... at least to me. 

[BRT-GTR]

       Again, got to agree, no signs of obvious wear.

   I'm still  convinced that these sections are broken out from the inside of the gear. The breaks look very much like brittle fractures such as you see in cast iron. So may be down to the metallurgy or heat treatment and a weak point created where the root of a ratchet V coincides with the root of an external gear tooth. Possibly a faulty batch of parts. Luckily, it doesn't happen that often, as far as I know.
       Brian, can't think of a suitable Joe Walsh line at this time. 11.45pm  here in the UK, Goodnight all.

[slawsonb]

I'm out here in the meadow
Part of an old stone wall
Stand here because he said so
Waitin' around to fall...
...bert
(one of my favs...)

[farmerdl]

Back in 1970 the local Bridgestone dealer replaced a lot of kickstart gears on new 350s with less than a thousand miles on them.  I seem to remember the word from Rockford was "improper heat treatment."  I had a new GTR at that time, rode it four years and never had a problem with the kickstart mechanism.  I have never had a kickstart mechanism fail while in use. (talk about asking for it,  have jinxed myself for certain) I have had a number of bikes that I have bought over the years come to me with broken starter gears.  I have always been pretty careful to take up the slack on the kickstarter and really just push it through the stroke.  I did notice back in the day from watching people start these little bikes that a lot of people would get up and jump on the starter like it was a '48 Harley. I am in no way saying anyone here is doing anything wrong, being heavy footed on the starter or anything else. The fact is that these bikes have been started a lot over the last 45 years and have maybe been abused a bit when starting, especially if they were not in the best of tune. Then again maybe Rockford's comment on heat treating may come in to play.  All speculation on my part, but I do know it was a problem even when they were new.

DL

[BRT-GTR]

           DL, Thanks for that input, it explains a lot and probably answers both Steve's original question and Moonpup's 'why'. Steve's GTO is one from the first production run in 69/70 and we all know Moonpup is a GTO fan.
    There was a break in 350 production from July 68 with the last of the red GTRs until November 69 when Gold GTOs came online for Rockfords, Seems quite likely BS made a new batch of starter gears for the 69/70 run and got something slightly wrong.
      I'm not saying these were the only starter gears to break but from what you say there definitely was an issue at that time.  So replace the gears, take it easy on the kickstart and everything should be fine.
      Another piece in the BS story jigsaw,   Brian.

[moonpup]

Steve's gear - 1970 GTO
Pup's gear - 1967 GTR
Bert's gear - ?? (I'm guessing a 1967/68 GTR)

[BRT-GTR]

          Yes, point taken        but I'm now satisfied it's the gear itself that self destructs due to kicking forces and is not some external factor (1970 more prone).

   I ran a late67/early68 GTR everyday for 3 years, must have started it 1000s of times with no problem.  Once primed the oil lines on the kickstart after a rebuild. Didn't want to start it without knowing the oil was through (fuel off, plugs out). Seem to remember it took 10-15 minutes. Just me being over cautious .
       So the answer lies in your own left leg.           Brian

[steve]

I really appreciate all the replies you guys have given, thanks...some very interesting responses there!

I have to admit Brian, I needed to read your initial very detailed reply a few times (and very slowly!) in conjunction with the manual, just so I could understand the operation and your theory. I think it's a good one and may very well be the answer. Actually, I did replace the ratchet pawl a couple of days ago but I need to remove it again as I'm still not convinced I've fitted it the correct way round...when I look at the end of my pawl, the angles are very subtle, certainly not as pronounced in the fig. 37 picture. I just fitted it as it had been previously fitted...the clue being a slight wear mark where the plunger rod has been pressing against it.

The one thing I'm not clear about is how the ratchet pawl is released automatically when the engine fires up, which would allow gear C to spin freely?? I keep looking at the pictures and reading the manual but the penny isn't dropping! However, as the gear breakage occurred whilst the bike was running, it does suggest that if the ratchet pawl was fitted incorrectly, it may well have been engaging with the gear (exactly as Brian said). Although as I mentioned in my first post about this, there were 3-4 separate occasions where the kickstart wasn't engaging at all (this had never happened prior to me doing this recent work). The gear wasn't broken at this stage so I can only imagine it was something to do with the ratchet pawl / plunger rod that was causing this...but I don't know what  ?? It worked immediately afterwards so the problem was only intermittent at that stage.

Just to add to the conundrum, it was interesting also to hear what DL says about this happening on low mileage bikes back in the day...you'd have to assume that the ratchet pawl on all these bikes were factory fitted and should therefore have been the correct way round. If it was due to 'improper heat treatment' you'd have thought BS would have sorted this out for the later models. My bike is from 1970 with only 3000 miles on it.

Steve

[steve]

The one thing I'm not clear about is how the ratchet pawl is released automatically when the engine fires up, which would allow gear C to spin freely??

Just been looking at this again...and I think the penny HAS finally dropped!

Steve

[moonpup]

....snip....   (1970 more prone). .....snip....

I think with this being so early in the discussion and with the limited examples given, this would be questionable at best....   

[slawsonb]

21U03456 is the bike the broken gear was taken from. Sept 67 build I believe.
...bert
(oh, and sorry for the JW digressions...;-)

[farmerdl]

I don't believe that all starter gears break for the same reason.  There is likely some small weakness in the gear's design that may have been exacerbated on those early painted tank models by a fault in the material. Those low mileage bikes I referred to were painted tank bikes while my first GTR was chromed, but those early painted tank bikes did seem to have more of a problem.  The point though, is that any number of factors can come into play. Any part can fail at any time. I just had a bearing fail in a piece of aeration equipment that  had run for only a few hours. I had a tractor just sitting idling and bang, it puts a rod through the side of the block.  And while it doesn't happen to everybody, I do believe that there is an inherent weakness in the kickstart gear.

[moonpup]

The 1967 GTR of mine that has the broken gear was a 5K mile bike that was put away in the shed because of a kick start problem.

This was obviously an issue long before the painted tank bikes came around.

Or... maybe this wasn't an issue at all and is just an unfortunate result from any number of factors including abuse, poor design, or who knows what. After all, we've all seen/heard stories of broken cranks and have kinda accepted that "stuff happens".