OP
UTC

Member
P150X 1980
Joined: UTC
Posts: 24
Location: Netherlands
 
Member
P150X 1980
Joined: UTC
Posts: 24
Location: Netherlands
UTC quote
Hi there, I am from Holland, new here and wanted to share some of my experience of my gearbox overhaul and discuss some issues which I am facing.

First of all I have a 1980 P150X which suffers from shooting out of gear, about once every 10km, mostly 2nd and 3rd.
What I already did:

-adjusted cables, helped a little
-replaced gear selector (small axle was having too much play) and installed a stronger spring: helped a lot, but not enough.

Furthermore at the moment I have opened the gearbox while having the engine still in the frame. I had a serious fight with the largest bottom bolt which apparantly was rusty. What I sucessfully did to split the cases was to place a big electric drill hammer on the bolt and gave it some serious beating. The cases magically opened. The bolt itself was a bit worn because of that and still inside the other side of the engine block, so I had to shorten it a bit and tap new thread. The outer case hole where the bolt was stuck in I drilled wider.

When removing the cruciform I noticed big play on the gears and a seriously worn cruciform. Also the inside of the gears were a bit rounded, but not awful much. I did not order new gears on forehand and wanted a cheap fix so I took a dremel with a tungsten carbide bit and sharpened 4 (out of 8, since not all 8 get worn: you don't drive backwards...) rounded corners inside all of the gears. I made sure every corner is straigt and the same amount is milled away. It's a bit of a guess, but I think it will work, the new cruciform fits nicely in it.

I ordered new shims for the gear play; one of 2,0mm and one of 2,1mm. However with the 2,1mm fitted there is still a play of around 0,5mm. So I either need a really fat shim or sand down the old shim (was already worn to around 1,5mm) and place that one in front of the new one to make them around 2,6mm together. Or order new (and thus thicker) gears, but I like to fix it the cheap way, after all I am Dutch. I also milled the hell out of the cilinder and piston to save some bucks on a cilinder kit

Anyway, in an old service manual I found that if you cannot fix the play on the front end where the circlip is you could also add an additional shim on the other side of the gears (just like you do with the newer models, which this one is not, it is from 1980, it even has the sprint gears in it; 54 and 48 teeth).

What is wise? Place an additional (thin) shim in the back, a double shim in the front, or a real thick single one in the front? How do I check or measure if the gears are in the exact correct position each time without closing the cases and build everything back together? Remember: the engine is still in the frame and I am not intending to open the clutch side. I can't really see if the cruciform is exactly in the middle of the gear when moving the selector rod.

Regards
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Addicted
Joined: UTC
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Addicted
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Welcome.You might get more responses in the Not So Modern section under the Forum button.
@jess avatar
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Petty Tyrant
0:7 And counting
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Location: Bay Area, California
 
Petty Tyrant
@jess avatar
0:7 And counting
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Location: Bay Area, California
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Moved to NSM.
@subetherbass avatar
UTC

Ossessionato
1997 Italjet Formula 125, 2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
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Location: Australa, Mate
 
Ossessionato
@subetherbass avatar
1997 Italjet Formula 125, 2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: UTC
Posts: 4814
Location: Australa, Mate
UTC quote
Photos will be helpful with diagnosing this.
Your main issue would have been the CRUCIFORM, as it's a common issue...as it's unlikely anything is wrong with the gears, they're pretty indestructible.
There is normally no reason to grind gears!

BTW: pretty sure there is a LEFT HAND THREAD bolt in there somewhere (big nut that holds shaft together?), so "loosening" it won't work.
@subetherbass avatar
UTC

Ossessionato
1997 Italjet Formula 125, 2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: UTC
Posts: 4814
Location: Australa, Mate
 
Ossessionato
@subetherbass avatar
1997 Italjet Formula 125, 2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: UTC
Posts: 4814
Location: Australa, Mate
UTC quote
SubEtherBASS wrote:
Photos will be helpful with diagnosing this.
Your main issue would have been the CRUCIFORM, as it's a common issue...as it's unlikely anything is wrong with the gears, they're pretty indestructible.
There is normally no reason to grind gears!

BTW: pretty sure there is a LEFT HAND THREAD bolt in there somewhere (big nut that holds shaft together?), so "loosening" it won't work.
Ohh, & WELCOME to the Dark Side!
There are some good scooterists where you are.
@orwell84 avatar
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Ossessionato
Joined: UTC
Posts: 3140
Location: northern New York
 
Ossessionato
@orwell84 avatar
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Location: northern New York
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I didn't know grinding gears was a thing. I get squaring off the rounded parts, but they are rounded because material has been worn away, so grinding away more material just doesn't seem logical, but someone with more knowledge and experience will correct me.
OP
UTC

Member
P150X 1980
Joined: UTC
Posts: 24
Location: Netherlands
 
Member
P150X 1980
Joined: UTC
Posts: 24
Location: Netherlands
UTC quote
Hello and thank you for all the quick responses, did not expect such a lively forum

About grinding the gears. See the attached picture. You can grind a little of the inner side of the gears to get a square shape instead of rounded/worn.

As a test for grinding a hard surface I even reshaped the old cruciform but since I already received a new one and the old one got pretty thin after grinding I threw that one away. But in theory it might also work.

But like I said; it was not much on mine, like a few tenths of a mm.
The important thing is that if you start doing this ( at your own risk, I have not driven with it yet!!) do all inner corners equally, otherwise the cruciform does not touch/scrape/press all corners equally.

Anyone has any additional thoughts about my actual shimming issue? Any experience with double shimming (/both ends) on a old style (single 2mm shim ) system? What about shimming more than 2,5mm in general? Recepe for failure or just fine?

Regards.
Forum member supplied image with no explanatory text
⚠️ Last edited by Scooba on UTC; edited 1 time
OP
UTC

Member
P150X 1980
Joined: UTC
Posts: 24
Location: Netherlands
 
Member
P150X 1980
Joined: UTC
Posts: 24
Location: Netherlands
UTC quote
Here is a video of the play of the gears and a picture where you can see the rotten bottom right large case bolt which I have beaten up with a jackhammer.

https://files.fm/f/gcgce7qa4

This method is actually suprisingly good and fast when you compare it with heating up with a blowtorch or drillilng it out completely. I can recommend that Laughing emoticon

You can vaguely see the bolt itself is a bit shorter, but it has new thread now. It will do it's job fine when using a washer less.[url][/url]
Forum member supplied image with no explanatory text
OP
UTC

Member
P150X 1980
Joined: UTC
Posts: 24
Location: Netherlands
 
Member
P150X 1980
Joined: UTC
Posts: 24
Location: Netherlands
UTC quote
Managed to shim the gears with a total play of 0,10mm this morning.
Used one 2,0mm shim and grinded down the original to 0,6mm with the below drill press. Used super glue to stick the original shim to the metal surface and with the grinding tool down and a horizontal swinging motion it took me about 2 hours with about 5 grinding papers.

The shim itself is flat, this method works pretty good as long as you swing to the left and right, (if your drill press allows this motion) otherwise it will round the sides and it will have an uneven thickness. I used 60 grid paper for 2 hours and WD40 lube. Ended with 400 grid by hand in a 8 figure motion on a piece of glass.

Placed both the 0,6mm and 2,0mm on the "normal" side behind the big circlip. Closed the cases and pushed and pulled the gear selector rod while using the kickstarter. It already felt much better.

Later I will place all the remaning components and then let's hope the rain stops pouring here, to go for a ride.

Think I will grind the cylinder head and cylinder top side this way too. I recently installed a self made extra thick bottom cylinder gasket to raise the ports.(My wife has a plotter machine, super easy to make gaskets in all kinds of shapes)
Also made a super thin aluminum head gasket, like 80 microns or something.

This way I hope to get a squish of around 1 to 1,5mm imstead of the ridiculous 3mm stock squish.

Regards
Forum member supplied image with no explanatory text
OP
UTC

Member
P150X 1980
Joined: UTC
Posts: 24
Location: Netherlands
 
Member
P150X 1980
Joined: UTC
Posts: 24
Location: Netherlands
UTC quote
This one can be locked, besides from a fuel starving problem it shifts fantastic with the replaced parts and mods
@pheasant_plucker avatar
UTC

Molto Verboso
bare metal cafe racer
Joined: UTC
Posts: 1379
Location: Aotearoa (New Zealand)
 
Molto Verboso
@pheasant_plucker avatar
bare metal cafe racer
Joined: UTC
Posts: 1379
Location: Aotearoa (New Zealand)
UTC quote
Nice work and perseverance! Welcome to the forum… thinking you will fit right in!

Now let's see some pics of your bike?

Yes - very active forum. And we love pics =).
OP
UTC

Member
P150X 1980
Joined: UTC
Posts: 24
Location: Netherlands
 
Member
P150X 1980
Joined: UTC
Posts: 24
Location: Netherlands
UTC quote
Tnx, realize now I got like plenty of photos from mechanical stuff and internals and only one from the actual outside Laughing emoticon
Forum member supplied image with no explanatory text
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