Gear Lash

[Guest Arie]

Being new to the spine frames I was wondering if the huge (IMO) gear lash is normal on them. Ive built a number of round heads (both loop and tonti) and never had a lash like this. My '83 SP NT is the tightest of all, there is no snatch and grab. My neighbor across the street says that he has the same with his Daytona. So whats the consensus, also it does needs the recall work to be done on the tranny, I have an appointment to bring it in to the shop in 2 weeks. I don't know if that has an effect on it or not.

[Guest ratchethack]

Arie, this is an interesting observation, and I reckon there's likely to be different takes on it. After having my trans out for the recall (I took it out and re-installed it myself and had the recall parts installation done "over the counter"), I was able to get a direct read on this by hand-rotating the input shaft with one hand with the other hand on the output shaft. My impression is that the actual lash within the trans is actually pretty low, about as low as can be expected, and that the lash isn't between gear teeth whatsoever. It's the engagement dogs in their slots. The new parts in the recall didn't change this in any way.

 

If you put the bike in first gear with engine not running, the bike will move ~10.5 cm forward and backward. This is the "lash" due to the dogs in their slots in the first gearset. I doubt if this can be reasonably considered a "huge" amount of lash. If you look at the driveshaft while you're doing this, you can see that there's also next to zero lash in the bevel drive, and there isn't enough force involved to get the cush drive to "flex" without loading it up in operation. If Guzzi had designed the gearsets with shorter slots and/or longer dogs, there'd be less free play, but shifting would get more challenging, 'cause then you're trying to hit a smaller high-speed target every time you shift. Earlier 5-speed boxes with 3-dog gearsets had easier shifting, but something like double the amount of slop in the engegement dogs, so I guess the 6-speeders are a whole bunch better!

 

IMHO, there are a number of things that contribute to the perception of excessive driveline snatch. Opening up the valve clearances to Euro specs (.004" and .006") or more (I run .006" and .008"), improving overall A/F ratios with a PC III (as many have done including myself) and just generally having the engine in a high state of tune all help quite a bit to alleviate low-throttle "bucking syndrome". One additional thing I did that improved things a lot more here - to the point where I no longer even notice it - was to convert the relatively abrupt stock 1/4-twist throttle to a 1/3-twist progressive throttle cam. I recently referenced a prior thread on this (see photos at post #10) at: http://www.v11lemans.com/forums/index.php?...topic=3961&st=0

[jrt]

Ok, and I'll give you my take- I have an Eldorado, a G5, and a Sport. The Sport has a LOT more lash (or snatch) than any of my other Guzzis. I don't know why, I don't know how to 'fix' it (if it needs fixing). It bothered me early on, but I've adapted to it.

[Guest ratchethack]

OK, where's Pete?

[docc]

Mine got worse and worse up until the new gearbox. Much better but still quite a lot. It really forces me to be smooth into corners.

[pete roper]

Unfortunately I don't have enough experience with the old six speeder to know what *acceptable* is. As Ratchet has pointed out the backlash is caused by space between the dogs on the gear pinions and the dogs on the sliding muffs. The greater the *gap* the easier it is for the dogs to engage so shifting, although it may not be *smoother* will be quicker.

 

Early five speeds all used a six dog engagement and when the box is set up right it works fine. The problem has always been that the boxes are built by production line workers, not mechanics, and the principle always seems to have been that as long as it will select all gears, no matter how poorly, then it's OK to push it out the door!!!!! Sport 1100C and some Daytona and Quota models and Centauros used a three dog engagement, which covered up the poor assembley to a degree but especially on models with no rear wheel cush drive the amount of backlash is so extreme that it beats the sh!t out of the pinion teeth, most particularly of 5th and inevitably on boxes with straight cut gears. It seems on the last Calis they have reached a compromise and gone to a five dog engagement system!

 

With the *old* six speeder options for setting up the change better are limited as there is nothing really adjustable. the selection is governed by geared cam-plates rather than an adjustable drum. Recent experience has taght me though that using the pawl adjuster can pay big dividends. I was also told by the tech-whizz at our local importer that taking out the cam plates and rigorously de-burring them along with carefully checking and cleaning the selector forks themselves can pay big dividends in improving the shift. Since the cam-plates can be accessed easily by simply removing the gearbox side cover it's certainly something I'd do to them when the return spring breaks, (as it's bound to do some time!).

 

If you can compare how much backlash you have in any gear with another bike. Any major difference and I'd be asking questions. Sorry I can't be of more help.

 

Pete

[rocketman]

Ratchehack,

I sure would like to have one of your progressive 1/3 throttle cams. Are you making them? Or, does someone manufacture them?

 

Rocketman

[Guest ratchethack]

Rocketman, I appreciate your interest. Many have asked me about this.

 

Coupla thoughts. Unfortunately, the reason I hand-fabricated mine was that I couldn't find a commercially available product - even one made for a more common application that could be adapted to fit. Odd stuff like this is fraught with problems: Since it takes a few hours of tedious fitting, whittling, and re-fitting to make each one, and making it a "drop in" replacement for the stock piece makes it harder yet, I had some time to think about this... I aborted 2 or 3 of 'em after hours of work in the process of getting it right, and I think I made 5 of 'em with different profiles by the time I wound up with one that I now consider ideal. I reckon the reason no one makes 'em is that the market would be so ultra-small as to make it commercially unfeasible. I figure most aftermarket moto products generally either have to have some kind of a high "bling" factor, they have to present some kind of a "go faster" advantage, or at least some kind of "boy racer" fantasy appeal (none of which this has) to justify the requisite high price of such a low-volume item - even if you standardized some tooling and popped 'em out in runs of hundreds each.

 

The reason I posted my photos was to encourage others who might be similiarly inspired to make their own, in view of the benefits, which I consider substantial. But of course that's just me and as always, YMMV.

[Skeeve]

... Since it takes a few hours of tedious fitting, whittling, and re-fitting to make each one, and making it a "drop in" replacement for the stock piece makes it harder yet, I had some time to think about this...   I aborted 2 or 3 of 'em after hours of work in the process of getting it right, and I think I made 5 of 'em with different profiles by the time I wound up with one that I now consider ideal....

64232[/snapback]

 

I hear you on the limited-scale economic realities being an obstacle!

 

Your statement above makes it clear (to me, at least) that it would be a huge benefit to anyone interested in making their own if you could post a picture of the "ideal" product. Not that I'm deriding the pics you've already provided in the original thread, but I mean something along the lines (no pun intended) of the snail on a sheet of 1/10" graph paper (or millimeter, whatever: just record the scale of divisions in the post w/ the pic.)

 

That way, we can all reasonably hope to replicate your results without having to repeat your extensive trial & error process [Ouch!]

 

Thanks for the help, even if you can't find the circular TUIT to post the pic...

 

Ride on!

[Guest Arie]

Ratchethack, Pete

Thanks for the replies. I was actually thinking on the same lines, I guess when people had the recall work done, the shops basicly set the selectors right. Thats my guess why people say the tranny work cleans up the lash. I'm going to try the larger clearances as well as I have to have the PC III A/F mix adjusted. This is funny to me that I have to bring this to a shop, because I haven't brought a bike in to be serviced since I bought my original Ambassador 20 years ago

About Skeeve's request...If you could even post your original drawing with a scale, I think we would all owe you a big favor!

 

Cheers

Arie

[Guest ratchethack]

Thanks for the help, even if you can't find the circular TUIT to post the pic... 

Rocket, Skeeve and Arie, here's a shot in situ . It's got a few thousand miles on it and it's the "final" rev.

[Guest ratchethack]

Gents, if you're actually motivated enough to whittle one of these out , I hope this helps. If I'd had this to work from I reckon it'd have saved me 4 out of 5 attempts. It's on 1/4" grid paper with the lines darkened in ballpoint pen so they show up. The material is 1/4" ABS. The throttle shaft slot had to be mostly carved out. I found that a dremel tool followed up with a very sharp knife works best. The seat area for the throttle shaft nut was countersunk to a depth of about 2 mm prior to cutting the shaft slot. Not shown, of course, is the cable slot. Best cut this shallow to start with and make it deeper as necessary to fit - a little deftness with hand tools and a bit o' patience with fittin' & re-fittin' doesn't hurt.

[rocketman]

Gents, if you're actually motivated enough to whittle one of these out , I hope this helps.  If I'd had this to work from I reckon it'd have saved me 4 out of 5 attempts.  It's on 1/4" grid paper with the lines darkened in ballpoint pen so they show up.  The material is 1/4" ABS.  The throttle shaft slot had to be mostly carved out.  I found that a dremel tool followed up with a very sharp knife works best.  The seat area for the throttle shaft nut was countersunk to a depth of about 2 mm prior to cutting the shaft slot.  Not shown, of course, is the cable slot.  Best cut this shallow to start with and make it deeper as necessary to fit - a little deftness with hand tools and a bit o' patience with fittin' & re-fittin' doesn't hurt.

64644[/snapback]

 

Thanks Rachethack. The picture and graph paper view helps. But, it looks like the graduated curve may still be hard to duplicate. Could you make a template? Trace the shape onto a piece of thick paper and mail it to me please. That way I would be sure to get it exact the first time.

 

Rocketman

[Guest ratchethack]

Rocket, let's see if I can help get you started here. I'd be happy to send you a template, but it wouldn't provide any more value than the photo with the grid. Keep in mind that the shape you see against the grid is only the periphery, it's a bit arbitrary, and that the important curve is the "working" curve that's unseen, described by the depth of the cable slot. Sorry, I ain't got a digital X-ray machine.

 

My experience has been that what's more critical here is the location of the cable-end socket relative to the slotted throttle shaft hole by distance and radial angle. The grid will allow you to get this spot-on.

 

You can assume that the hidden line that would describe the cable slot would run through the center of the cable-end socket, and that it would taper off, roughly following the peripheral curve to a decreasing depth that clears the large "lightening hole". As I suggested previously, best cut the cable slot shallow to start with and go deeper to fit by trial and error, fine-tuning with the cable adjuster at the twist grip.

 

Not to discourage you, my friend, but if you find it too tedious to transfer points from the photo grid to your own grid, you probably shouldn't attempt this fabrication, 'cause this'd be the easy part. Hope this helps. Any more questions, fire away.

[dlaing]

Any more questions, fire away.

64679[/snapback]

Awesome job John!

What are your thoughts concerning the increased cable drag due to increased angle?

Would you consider an even bigger wheel or do you think you are close to the limit of acceptible cable drag?

I suppose regular lubing becomes more important.

I searched for a smaller throttle pulley (at the handle bar) but did not find anything.