Squish for TZR 125 DL3 RR Belgarda

[Chris_]

Hi folks,

i have a little problem while mounting my new 3mboo cylinder ( O-Ring-Conversion) on my DL3 RR.
Did anyone of yours know how tight the original squish (c-head) is? 1,3 mm or 1,5mm or higher.


Problem is......mounting o-ring-barrel with oem yamaha foot gasket 0,55mm, squish is 0,8mm/0,9mm. The engine sounds not healthy, you can hear loud knockings at the top of the engine.
Then i have installed a 0,9mm foot-gasket, squish now is 1,2 - 1,3mm but the engine sounds better but i hear engine-knocking at reving too.

The o-ring barrel no need a head gasket ( -0,25mm ), that means for me, i have to add these lost 0,25mm to the cylinder-foot-gasket....

I have done it with a 0,90mm foot-gasket but engine sounds strange at idling.....

I dont know where the failure is ! Piston is a new meteor one and fits, crankshaft is tested and ok. Before changing the piston ( no o-ring-conversion) the engine runs well without knockings....


Maybe anyone know the original squish rate or have any ideas why the engine sounds bad ?


Cheers

Sorry for my bad english tongue

[SpookDog]

Have you checked the head and piston top for damage? Also the small end bearings? Spark plug to piston clearance?

[SpookDog]

Can you please tell me if the 4DL (gold) fork top tubes are aluminium, or just galvanised steel?...

Cheers bud!...

[SeaR1ck]

Does a magnet stick to them? Yes = steel aluminium = no

[Gooch]

41mm Paoilis, no?  Hard anodized aluminum top tubes.

I bought some from a SZR which I had to have reanodized.

[SpookDog]

I have a 4hw with steel tubes USD's
I was wondering about the gold coloured tubes on the belgarda? 39mm I think, not the gas adjustable SP ones...

[Chris_]

Hi folks,

thank you for your replies and sorry for late response.

@Spookdog... yes i have checked the parts again. No damages or contact-signs located at piston, cylinder, crank or conrod.

Forks: The 4HW (4FL) version have a different fork with 39 diameter, at the Belgarda DL there are mounted the golden Paoli ones with 41mm.

@SeaR1ck ...I´ve never tested it with a magnet but it looks like that my golden RR-forks was made from aluminium. I will check it out in near future.

Back to my engine problem:
I have talked to a good old yamaha 2 stroke mechanic and he told me that a squish from 1,2 to 1,3mm is nearly original. At the english DT-Forum i have found a guy who has made the o-ring-conversion too and he wrote that the original yamaha 3mboo squish is about 1,35 +-mm. That´s it !

The 2 stroke mechanic advice me to fuel in high octane petrol (Aral Ultimate 102 Octan) but i makes no differences. Engine sounds bad again, no wonder, the engine is not compacted now with the 0,8-0,9mm base-gasket. The higher octane-fuel should be used for high compressed engines....
I think the lower conrod bearing makes some noises. That means...i will repair the whole engine through the winter period.

Yesterday i have startet the engine again. Big white clouds coming out of the exhaust.... the o-ring at the top head is leaky  .

For this year i am fed up with the 125cc TZR. Now i will repair my Yamaha TDR 250. After engine rebuild for 1,5 years an oil hose was buckled and i have dont seen it. After 250 km riding the right piston has blocked. Now the faulty cylinder was checked and honed and a new Mitaka piston is waiting for mounting.

Cheers

Chris

[SpookDog]

If I was you, I'd put 2 standard base gaskets on and replace the o-ring...

If it's making any top end noises after that I'd try uploading a short Utube clip so people can hear exactly what it sounds like...

It's not a huge job, and I can't imagine the big end bearings letting go before the small end does...