50mm taiwan bore info

[evilone]

I'm posting this due to madman and i both having similar problems (soft-seize) with similar builds.

Took my cylinder off which i was told had less than 200 miles IIRC.

1. Ring gap is .01"-.02" when it should be closer to .10"
2. piston to cylinder clearance was .002" (not too bad).
3. there are signs of excessive blow-by on the piston so i need to hone to make sure cylinder is round.
4. some of the ports had very little chamfer and exhaust port has zero chamfer.

So...i'm honing the cylinder, putting chamfer on ports, and fixing ring gap. Also going to bevel the piston skirt.
I'll post results later.

Just a F.Y.I for anyone planning on running a 50mm Taiwan bore. And to backup what bakaracer has stated .

[Red Eft Performance]

Good info these are some basics that are never talked about on these forums.

In the 2 stroke world in general a lot of bores dont come with the ports chamfered. This should be done by the installer. In our world The only bore I know of that comes with the ports chamfered from the factory is the Malossi MHR.(If there are others feel free to correct me)

So all the rest should be chamfered.

http://www.youtube.com/watch?v=bFkpxW4x ... xt=1&list=

[Madman]

The ring gap on mine is way too small just visually it's too small, I should have not assumed that it was correct even though I bought it as a kit, piston clearance is also questionable but the ports had been beveled ! But I must have a air leak someplace to "soft seize" like I did!

[bakaracer]

ring end gap should around .010-.014 . Up to .018 is limit. The reason why I say run a hone through a new taiwan bore is because a lot of then the bore is not round and has some high spots. Plus a lot if not all don't come chamfered in the ports. The piston bottoms are not beveled either.

[Majourlittle]

As confirmed by Darin, The Tiawan bores lack a considerable ammount of QC. In fact the piston that I had in my Tiwaneese bore was much bigger at the skirt than at the dome. I believe that if I had run the bore withought checking this beforehand, I wold have soft seized under normal running conditions.

[bonesv]

As confirmed by Darin, The Tiawan bores lack a considerable ammount of QC. In fact the piston that I had in my Tiwaneese bore was much bigger at the skirt than at the dome. I believe that if I had run the bore withought checking this beforehand, I wold have soft seized under normal running conditions.

Just curious as to how you remedied that piston issue?
And was there anything else you did to the cylinder other than the above suggestions?
Thank you for the help.

[bonesv]

2. piston to cylinder clearance was .02" (not too bad).

Evilone, you mean .002 two thousandths.

[evilone]

Yes .002, 2 thousandths. Edited.

[Red Eft Performance]

As confirmed by Darin, The Tiawan bores lack a considerable ammount of QC. In fact the piston that I had in my Tiwaneese bore was much bigger at the skirt than at the dome. I believe that if I had run the bore withought checking this beforehand, I wold have soft seized under normal running conditions.

pistons are larger at the skirt than the dome. When measuring a piston you always measure it just up a little bit from the bottom of the skirt 90 degrees out from the pin. You measure in this location cause typically it going to be the largest point.

[Madman]

How about this?

[Mystic]

wow that is definately not true round, possible reason for seizure??

[damnSA50]

is that the piston ring?

[Madman]

is that the piston ring?

yes it's the piston ring. The gap is the main point! The cylinder is round it just looks distorted in the photo!

[Fishman43]

yes it's the piston ring. The gap is the main point!

Do you have a set of feeler gauges to check the gap? It is really hard to get a sense of the small differences (tens to hundredths) by eye.

[bakaracer]

You have to check with a feeler gauge to make sure what the gap is at. But just by looking from your pic ,that looks like its more than enough. My guess is .013