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The TTR250 FAQ web pages -> TTR250 -> Modifications -> Wiseco +2mm 263cc kit and porting cylinder head
Post Info TOPIC: Wiseco +2mm 263cc kit and porting cylinder head
Tarbone


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Wiseco +2mm 263cc kit and porting cylinder head
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Hello everyone!

 

I'm about to have my barrel machined out for a +2mm OS wiseco kit. I was just curious if anyone could chime in on reliability thus far? I'll be running the stock liner.

 

I know there are a few posts about this kit but was curious how impressions may or may not have changed?

 

Thanks!

 

-Matthew



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Kaos


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Wiseco +2 kit.
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Hi Matthew.

Timely post, mine is in the shop right now now getting the same done . Same piston as you, + 2mm wiseco.


My barrel and piston is done, just waiting on the head to come back from the machine shop, it's been skimmed to raise compression. (Apparently the 10.5 : 1 piston didn't make 10.5 : 1 compression)

Should be ready in at week or so, just some head porting and tuning.

Reliability should be similar to stock. (supposedly!!)

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Tarbone


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That's awesome, great minds think alike! 😂

Do you know much material was actually removed to get the final compression ratio of 10.5:1?

I have been working my head as well, I finished polishing the combustion chamber and have been working on porting the intake and polishing the exhaust.

IMG_20170202_185244_171.jpg
Cheers!

-Matthew



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ttr steve


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Looking very nice!

Great feedback guy's smilesmilesmile

We all love this type of info headbang.gif



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petenz


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That looks good...
got any pics of the ports...


.

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devon_rich


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Cant comment on the +2, but I have thrashed a +0.5 for the last two years and all is well

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Tarbone


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Pics don't do it justice. Exhaust port doesn't look smooth in the pic. The port is opened up a little bit with a flex shaft tool and then hand polished with wet sand paper up to 1200 grit. I flowed smoke through before and after. A lot less turbulence. I could work that side for hours but I'm satisfied for my own liking. 

20170203_231157.jpg



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petenz


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looks good....
something i will do to mine if the motor ever
gives me a reason to take it apart..
dosn't look like going to happen any time soon..





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Kaos


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Thats looking good Matthew
I'll be very interested to hear your thoughts about how she runs.
Tarbone wrote:

That's awesome, great minds think alike! 😂

Do you know much material was actually removed to get the final compression ratio of 10.5:1?

I have been working my head as well, I finished polishing the combustion chamber and have been working on porting the intake and polishing the exhaust.

 

I don't exactly know how much they skimmed off the head.   Thats all a bit technical for me.  

All I know was that they assembled everything and measured with Plasticine, and calculated it was not 10.5:1.   It might have been about half a mm or so?? to get it to 10.5"to 1. I'll make a point to find out,

Anyway it should still be a little bit of a boost I think 10.2 is standard.  

Its still to be ported and now I'm waiting on a carby to arrive and a dyno tune.  Getting impatient now.

 

Let me know how yours goes. 

 

 



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petenz


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devon_rich wrote:

Cant comment on the +2, but I have thrashed a +0.5 for the last two years and all is well

 should be no issues as they are just standard Yamaha over sizes...

10.5:1 is still a pretty mild compression ratio..



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Tarbone


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Here's a little better picture. Light is better. 

20170204_185316.jpg



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Kaos


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Nice. When will you put it back together?

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TTRfan


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I love shiny aluminium engine parts biggrin

I haven't tried porting a head but my recollection is that the first thing to do on a TTR is to match the inlet stub to the head so that the head casting doesn't project a sharp edge into the flow of incoming mixture.

Brian 



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Tarbone


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Kaos wrote:

Nice. When will you put it back together?

 Right now 😃

Everything looks perfect. Got the jug and piston back from the machinist today.

 

20170207_174908.jpg



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TTRfan


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Looking good!

I have managed to survive all these years with just a couple of different-sized Vernier calipers and have always meant to buy the tools to measure the internal bores and the pistons but never got around to it.

I just took the easy, but expensive, way out and rebored all my rebuilds and fitted new pistons!

OK - showing my ignorance , what exactly are the two tools in your photo and what ranges do they measure please?

Brian



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Tarbone


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TTRfan wrote:

Looking good!

I have managed to survive all these years with just a couple of different-sized Vernier calipers and have always meant to buy the tools to measure the internal bores and the pistons but never got around to it.

I just took the easy, but expensive, way out and rebored all my rebuilds and fitted new pistons!

OK - showing my ignorance , what exactly are the two tools in your photo and what ranges do they measure please?

Brian

 Hey Brian, 

 

Vernier work fine! I was a machinist for about 12 years, I just happen to have all the goodies 😎

 

You're looking at an outside micrometer and an inside micrometer. 

 

That particular set has a size range from 0-4" O.D. and 1-6" I.D. 

 

For any sizes smaller than 1" I.D. I can use telescoping gauges. 

 

Motor is back together btw! She fired up first try. It's snowing here currently. No riding to break her in..

 

Cheers!



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Tarbone


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Hey there fellas!

Quick update. Motor is all back together and running like a top. I dropped the oil at 50 miles and am almost at 100. I'll drop the oil again a few more times at 50 mile intervals just to make sure she's got fresh juice in the bottom end!

Question for those with this mod. I decided to do a hot compression test today with almost 100 miles on the clock. I'm getting 205!!? Should I be concerned?

Thanks in advance!

-Matthew

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TTRfan


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Looking at the manual, Yamaha quote 174psi at 300rpm so 205 is quite remarkable!

Is there any sign of pinking (pre-ignition - where the engine sounds like it has a bag of nails in the combustion chamber when you wind it on) or over heating?

If not, then enjoy the extra horses. Maybe dyno it when run in wink

However, I confess that I thought the Wiseco was the same compression as the standard piston confuse

Brian



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hanzo


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The yamaha heads are pretty rough casting wise on the TTr from what ive seen so even a mild port and polish would improve things in my opinion .There is quite a bit of material in there a freind did mine when I changed the valve stem oil seals .Yours looks very well done nice work wink



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