Casa 185 / RT195 piston edge (deck?) to Exhaust port height

[Pompeydave]

Still struggling with this problem albeit on a different engine with an RT195 kit. I can get the edge of the piston in line perfectly with the bottom of the exhaust port but the transfer ports are just slightly lower than the piston edge. Is this a good level for a torquey setup?

I'm using a 60mm crank and 110mm rod by the way for maximum flexibility so I can play about with it quite a bit if need be.

[Grumpy225]

Still struggling with this problem albeit on a different engine with an RT195 kit. I can get the edge of the piston in line perfectly with the bottom of the exhaust port but the transfer ports are just slightly lower than the piston edge. Is this a good level for a torquey setup?

I'm using a 60mm crank and 110mm rod by the way for maximum flexibility so I can play about with it quite a bit if need be.

That's fine

[garry inglis]

on the rt kit you want piston level with both ports witch should put it 0.5 to 1mm below ex port that's how mb explaines how to set it up I have just built two kits up at this setting with great results you can try the 0.5 or 0.7 base gaskets and no head gasket should get you a nice squish of 1.2 1.3 or with the 110 rod you have 2.5 or 3mm packer to play with

[Pompeydave]

Ok, thats what I had when first setup. Looks like i just need a 0.5mm head gasket to get a 1.3 squish. Cheers for the advice..

[olliewtf]

seems there's a tad bit of confusion in the original post.
deck height is the difference between top of piston and top of barrel.
inputting this into a porting calculator plus measurements of the distance between top of barrel and top of (or bottom of with regard to inlet) your ports will give you your port timings. with this info some can offer advice for what would be the best set up for whatever you want with regard to manipulating the timings with base gaskets, you can see the changes as it affects your deck height.
You should then also consider, if you fit x base gasket for desired timings, where your piston is in relation to exh and trans ports at bdc.
I work from the understanding that if your piston sits below the bottom of the exh port, it can cause heat build up and overheat your crown.
this is something i read on a forum and agree with, though i have no experience of its real life affect.
hope that clears things up, and if ive misread your OP and said alot of stuff you already know, apologies!
best of luck

[Pompeydave]

on the rt kit you want piston level with both ports witch should put it 0.5 to 1mm below ex port that's how mb explaines how to set it up

Well, if the crown overheats if below the exhaust port at BDC surely MB wouldn't recommend that setting? Garry, do you know where MB state that this is the way to go on their website?

[garry inglis]

if you look at the rt kit for sale and below is all the setting up advice this is on mb site

[garry inglis]

my fault said it the wrong way the piston level with tran ports should set it 0.5 to1mm above export typing and thinking at the same time derrrrrrrr

[shamrockexpress]

this was the position i had to settle with my recent GT186 set up, this has the piston .7mm above port at bdc as can be seen, the reason for this is i have a 110 rod which normally would have involved a 3mm packer, for some reason i ended up with a 1.5 mm packer and i had 3x .35mm gaskets giving me a total of 2.55mm so with a dry build and no more gaskets left i was ending up with 1.0mm squish!!! too close for comfort, The piston has since ended up as it is in the pic. .7 mm this i liked also the transfers were nearly clear (to look at with the eye) so the choice!!!! its a case of order up a 2.0mm packer or put .5 head gasket on and carry on,,,,,,,,,,,,,,,,so on with the head gasket and an even squish all round 1.54 so happy with that so i carried on with the plan to strip and add the packer after a 1000 miles and do away with the head gasket and see what the difference is so hopefully this will give me an insight were the piston should be at BDC will also give me a good look to see how the kit is holding oil and compression, ring gap changes.............done a leak down test and all is good 200 miles so far its starting easy and pulling strong, i will be surprised when i do the change if there was any more power to be had this would be a bonus..........
BTW remember i have lifted the exhaust port 1.0mm so if i hadnt ve done this then the transfer timing would not be so good...

[Pompeydave]

Ah, interesting stuff, cheers chaps. I'm still confused re whereabouts the piston should ideally be at bdc. My RT195 is a Scooter Center Koln supplied one- I'm sure I read somewhere that the port timings are different between the MB supplied kits and those from Scooter Center- any ideas anyone?