second gear jumping

Moto Rumi technical problems or solutions
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dthomas
Posts: 150
Joined: Tue Dec 29, 2009 9:09 pm

second gear jumping

Post by dthomas » Mon Mar 28, 2011 9:47 pm

Hi when i first rebuilt my engine my gears looked and :cry worked fine but i had problem and had to strip it down again
and now it keeps jumping out of second gear could this be anything to do with putting the side casing back on in the correct position or something of a bigger problem
Cheers David

Lasse
Posts: 1501
Joined: Mon Aug 10, 2009 5:18 pm

Re: second gear jumping

Post by Lasse » Tue Mar 29, 2011 9:08 am

You are absolutely right - it "has something with putting back the clutch cover in position" to do!
But I am afraid, that you have a lot of troubles ahead, because the shifter mechanism is VERY sensitive to even the smallest (wrong) movements of various things...
So I ask: did you in any way move the selector drum (by loosening the two outside screws?)

If not, you could be lucky enough, to get the gearselecting mechanism work as before.

Did you change any of the gearwheels or rollerbearings?
Did you file any of the pawls?
Did you change /open the slots under the pawl mechanism?

If no to all of the above questions - its "just" the way to position the clutch cover right, you have in front of you!
Try the "good old 4.th gear method" first - its most likely it will work.
(Put the box securely into 4.th gear - then press the gearpedal as you would do, when changing up to 4.th gear (the curved toothed quadrant just touching the uppermost inside part of the clutch cover)
Carefully put the clutch cover onto its proper place, WITHOUT letting anything of the mechanism move!

Secure the cover and do a (very) short testdrive, witout oil in the box - provided that you have oiled all the gears beforehand with some heavy oil.
(Dont forget the small steel-ball at the end of the clutch mechanism)

I can tell you, that I had all sorts of trouble myself, with the gearbox,because its not the easiest box to get right, if it had started to make trouble.
But I will help you as best I can - & dont forget Paul Stokes, he is an expert on the RUMI box as well...


Have Fun,
Lasse.

dthomas
Posts: 150
Joined: Tue Dec 29, 2009 9:09 pm

Re: second gear jumping

Post by dthomas » Tue Mar 29, 2011 8:40 pm

Hi Lasse Thanks for the info yes i did remove the selector drum but i put it back in the same position as far as i know .I will try the 4 gear option and see how it go,s if I have no luck should i try the selector drum in a different position

cheers David
ps it do not all ways jump out of gear it happens more when I try to accelerate

Lasse
Posts: 1501
Joined: Mon Aug 10, 2009 5:18 pm

Re: second gear jumping

Post by Lasse » Wed Mar 30, 2011 7:25 am

Before I got my box right ,my "slip-offs" of second gear, ALWAYS just happened under acceleration!
You simply cant imagine, how very, very small changes of the selector drum position, can result in misfunction of your gearbox...

Funded on what you say now, its (almost) certain, that the slip-offs of second gear, stems from your "playing around" with the selector-drum position!
As I say, just TINY movements of this drum, can be critical.
I am afraid, that the only remedy here is "trial & error" - (for my part, I spent most of one day sweating and swearing, BEFORE I suddenly got it right...)


Lasse.

formic
Posts: 203
Joined: Fri Jan 08, 2010 3:52 pm

Re: second gear jumping

Post by formic » Wed Mar 30, 2011 10:05 am

Hello dthomas, there are previous postings on this subject,to which you should refer.
In my view the expert is Mr Skinner.Good luck we have all been there.
Michael

hugomez
Site Admin
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Location: Amsterdam
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Re: second gear jumping

Post by hugomez » Wed Mar 30, 2011 12:09 pm

formic wrote:Hello dthomas, there are previous postings on this subject,to which you should refer.
In my view the expert is Mr Skinner.Good luck we have all been there.
Michael
Hi Formic, could you please posting here the link to the topic you are talking about?, then will be easier for dthomas.

However, I take the opportunity to remind everyone that we have a "Search" tool in the top right side of the page that will help you to find old topics easily.

;)
OO
My little Formichino here: http://www.formichino.com/pictures1.html

formic
Posts: 203
Joined: Fri Jan 08, 2010 3:52 pm

Re: second gear jumping

Post by formic » Wed Mar 30, 2011 12:44 pm

Hello everyone,a look in 'technical:questions and solutions' should find a thread beginning The Holy Grail of---

This one: http://www.formichino.com/forum/viewtop ... f=17&t=126

Cheers
Michael

Ian Skinner
Posts: 539
Joined: Mon Aug 24, 2009 12:36 pm
Location: South Wales UK

Re: second gear jumping

Post by Ian Skinner » Mon Apr 04, 2011 4:28 pm

Hi there, you Rumi gearbox enthusiasts? Just a few comments which I hope you will find interesting.

In my spares collection I have 22 selector drum brass bushes, some used, some new. Of those used, only five have 'nurdled' retaining holes i.e. manually slotted post production allowing adjustment as outlined in some previous forum submissions.. I must say that I have never found this necessary in the many gearbox builds that I have carried out, any adjustments being made to the gearbox internals or the external selector mechanism.

Also, I have a fair number of selector drums and idler gears, again some used, some new and some of them with ancient price tags showing that they were sold singly and not paired. Having inspected them all, I can report that all the ground markings are identically placed on each type, indicating a production process and not an assembly performance.

To my knowledge , the only paired components in the transmission are Section 11 Item 50 (69-439) and Section 12 item 45 (62-378), probably for backlash adjustment during production assembly. Some of you will have noticed the coloured paint blob markings, if they are still there on yours.

Gear jumping problems after crankcase assembly when none occurred previously in owners machines that I have helped solve were caused in the main by:-

• Gear shaft bearing(s) not butting up to stop rings.
• More than 60 thou clearance between the face of Section 12 Item 27 (9973) and the dogs of Section 12 Item 26 (8828a-9).
• Loss or incorrect shimming of the selector drum.
• Binding selector drum, no end float.
• interference of the selector drum end with the selector control quadrant.
• Broken or no spring under the gear stop plunger Section 12 Item 16 (n8843-39).

Progressive gear jumping problems with machines in use is entirely due to wear and predominately affects 1st gear, which shows up under harsh acceleration and hill climbing. The specific problem is the decreased depth of pressured penetration of the dogs Section 12 Item 26 into the slots of Section 12 Item 27 during 1st gear engagement. This is caused by the accumulated slop in the gear selector fork spindles and pivots, and to a lesser extent, wear of the fork faces. There has to be reasonable clearance on the pins working in the cam of the selector drum but it does add up. Any rounded drive sides of the dogs of Section 12 Item 26 don't help but as such are little cause of 1st gear jumping! I've seen plenty like it in Suzuki RG500 boxes and they don't jump! However, I'm told angular under-cutting the dogs of 26 and the slots of 27 has been used by others with some success,. (Tony has always liked this idea!) So, replacing all of the selector fork components or having their bearing surfaces plated up and ground, is the best way forward. What else can be done? Well, it is possible to shim over the selector drum towards the brass bearing, maybe as much as 15 thou. This will close the clearance between Section 12 Item 27 and Item 26 to an acceptable gap when the slop is loaded up. The negative is that the dog penetration of 2nd, 3rd and 4th gear is reduced, mainly 3rd. However, 50% works ok, there is slop there as well which is taken up by being drawn in the other 50% under load, by the dog's factory angled undercut sides. I sorted my Formichino Tipo Sport gearbox successfully this way nine years ago and a fair number of others since. However, a word of warning, watch out for any clash with the end of the selector drum and quadrant. If there is, fresh or re-worked selector fork components is really the proper way forward. On the other hand, you could completely shim all the gears for perfect engagement, better to buy a new Vespa 300 perhaps!!

One other thing, the fourth gear engagement method of gearbox side placement does not always perform as advertised. If this happens to you, be pleased to refer to the Moto Rumi Club site where they have my long standing instructions on how to do it in the Technical Section.

Ian

Ian Skinner
Posts: 539
Joined: Mon Aug 24, 2009 12:36 pm
Location: South Wales UK

Re: second gear jumping

Post by Ian Skinner » Mon Apr 04, 2011 5:06 pm

Hi there, for clarification.

The 60 thou clearance to which I refer is the gap between the end of the dogs and the flat sided 1st gear, when the gearbox is in the nuetral state.

My gearbox side cover placement method on the Moto Rumi Club site is the quadrant alignment method including the schematic, not the 4th gear method which is also shown.

Ian

dthomas
Posts: 150
Joined: Tue Dec 29, 2009 9:09 pm

Re: second gear jumping

Post by dthomas » Fri Apr 15, 2011 11:16 pm

Hi rumi guys
first of all thanks to ever one for your help with my gearbox blues.Today i tried the selector in more positions than the kama sutra the rubber bands the forth gear method ,the five fingered monkey method and we are still occasionally jumping out gear ,so i have decided for now i will live with problem call it my little ghost in the machine
Ta David

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