Finally time for a rebuil!

ProjectBlasturd

ProjectBlasturd

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Oct 30, 2017
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Well fellas, today was the day lol. Finally smoked my top end riding out in the snow lmao. Lost alot of compression and I'm also pretty sure I blew out my crank seal. Just bought a Athena top end gasket set, Wiseco bottom end seal kit with clutch cover gasket, some yamabond 4, anddddd Tusk rear wheel spacers just for the hell of it :D Gonna pick up one of these bad boys too while I'm at it:
https://www.ebay.com/i/202099879831?chn=ps&ul_ref=http%3A%2F%2Frover.ebay.com%2Frover%2F1%2F711-117182-37290-0%2F2%3Fmpre%3Dhttps%253A%252F%252Fwww.ebay.com%252Fi%252F202099879831%253Fchn%253Dps%26itemid%3D202099879831%26targetid%3D382087756475%26device%3Dm%26adtype%3Dpla%26googleloc%3D9021977%26poi%3D%26campaignid%3D936468908%26adgroupid%3D47758128158%26rlsatarget%3Daud-384261918427%3Apla-382087756475%26abcId%3D1129676%26merchantid%3D107452102%26gclid%3DCjwKCAiA7JfSBRBrEiwA1DWSG52gc2dVHbt3WERAqVq7Aljsv4t9oX19H-ygMh3b6_RncsMIfZgUXRoCopsQAvD_BwE%26srcrot%3D711-117182-37290-0%26rvr_id%3D1404435621600

Then I'll work on everything else until spring comes when I can properly jet the bike for normal weather. I already have a good little pile of parts for now. New DG National front bumper, Alba rear grab bar, Maier Front race plastics, new rear plastics (going to blue btw), 14-40 sprocket set. I'l put all of it on day by day. Beadlocks are on the way, still unsure if I want the diamond j widening kit up front or the alba a-arms, And possibly going with a DMC Alien pipe kit if not a dynoport or Shearer. I'l keep everyone updated along the way and ask qestions when I need to though :cool:
 
Only thing I see is that a 68mm is NOT a big bore. It is a stock cylinder on its last bore. When it wears out it's junk.
Why not do a fresh bore/new piston on your existing cylinder ? Have it measured at a shop that will be boring cylinder. You need to have the piston on hand before boring so it can be fitted for proper clearance.
Do not get a cheap eBay cylinder/piston kit, they are proven junk !!
 
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Larry's Shee said:
Only thing I see is that a 68mm is NOT a big bore. It is a stock cylinder on its last bore. When it wears out it's junk.
Why not do a fresh bore/new piston on your existing cylinder ? Have it measured at a shop that will be boring cylinder. You need to have the piston on hand before boring so it can be fitted for proper clearance.
Do not get a cheap eBay cylinder/piston kit, they are proven junk !!
Click to expand...
Because there aren't any shops by me that do it (that I was able to find anyway). Can you explain the difference between a 240 and the link I posted?
 
Larry's Shee said:
Only thing I see is that a 68mm is NOT a big bore. It is a stock cylinder on its last bore. When it wears out it's junk.
Why not do a fresh bore/new piston on your existing cylinder ? Have it measured at a shop that will be boring cylinder. You need to have the piston on hand before boring so it can be fitted for proper clearance.
Do not get a cheap eBay cylinder/piston kit, they are proven junk !!
Click to expand...
If it's only bored to a 210 then isn' there still room to go to a 240? I' confuzzled
 
A 240 bore would start at 72mm (airsal at 71mm), not 66-68.25 bore which would be just over boring your cylinder for nothing. He is taking a junk china niche cylinder and over boring it for no reason and advertising as a big bore. You only have 1 bores left and if you gauge it deep enough that cylinder will need a sleeve. He got you!!! That is no where near a big bore kit and is falsely advertised imo. I would return that junk asap. You could send your existing cylinder to Ken for a bore, order a piston, have crank rebuilt for about the same money and be miles ahead. Not trying to ruin your parade but that cylinder will be fried in no time.
 
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http://performancetrends.com/Calculators/Engine-Displacement/Engine-Displacement.php


use this link and should help you better understand. A stock cylinder sleeve is only boreable to 68.25 without getting a larger sleeve which is not really ideal on a stock cylinder. Technically that new cylinder would be 207cc.

Change the measurement units to mm, and displacement unit to cc's. Put in your new cylinders bore 68.00mm, your stroke which is 57mm on a stock crank and you get 207cc. Even on max bore at 68.25 you are only at 208.5 ish....

You will get way more power on a ported stock cylinder any day over a big bore unported cylinder. Over boring for more power is not the way to go. Very very little power difference.
 
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So I got my top end apart. Not as bad as I thought, but still sucks lol. Let me know what you guys think. Here' some pics and a video
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20171230_095919.jpg
 
The movement between piston and rod is normal. The rod/crank is a different story. Up and down play is measured with a dial indicator, tolerance being nearly zero. Maybe .0005" , check the repair manual.
Side play between rod and crank is pretty small and is measured with a feeler gauge. IF you have any doubt have it checked out by a shop/dealership.
My old eyes can't tell much from pics, but the bore looks awful smooth, no crosshatch.

As mentioned, a stock cylinder ( Yamaha) beats any after market cylinder.
 
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BTW, there was a thread about those cylinders when they first came out. Very poor quality. Pourus sleeves when bored, and extremely short engine life. I have also wondered about the hardness of the sleeve. But none have lasted long enough to know.


You have to wonder when they can sell a new cylinder, piston, and gaskets for less than what a Wiseco piston costs.
 
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Also the big question would be the run out in the crank. Its tough to tell when in the cases as the bearings could have movement etc. The only true test is to get it out and on some centers. Although a quick test to at least give you an idea is to take the piston off the rod, then slowly spin the crank watching the gap on each side of the crank (between cases and crank web), you could use a feeler gauge if you wish but not necessary. You will see if it gets larger or smaller in some areas and if it has any difference typically it should be checked.
 
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Tough to tell for sure in the pics but the bore does look pretty glazed along with some scoring marks. Take a few more pics but one going down/up exhaust side(where pipe would connect) and one down/up on intake side (carb/reed side). Maybe a bit less light to. lol Basically we want a pic to look like exactly as you see it.
 
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There is a good bit of movement from the rod on the crank. Not crazy amounts but she has a tiny bit of wiggle from side to side. And here's a pic of the cylinder through the exhaust port
15146794305622022360557.jpg


And from the bottom of the cylinder up with less light
1514679575332391912302.jpg
 
Well I still see some cross hatch in the bore, although it doesn't look like the best chamfer job. Tough to decipher from the pics. Look at all that meat on the sleeve. Perfect porting candidate!! And 1000 X's better than niche.
 
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sooo how much compression was lost?
or do you just want some newer parts:D
don't buy cylinder gimmicks off e-bay
what did you actually experience riding in the snow?
I'm sure it got hot as hell
what is the bore on your current cylinder?
do you at least have a digital calipers/or feeler gauges/or a compression tester?
30 bucks for comp gauge/digital calipers the tools will tell you:)
 
ProjectBlasturd said:
There is a good bit of movement from the rod on the crank. Not crazy amounts but she has a tiny bit of wiggle from side to side. And here's a pic of the cylinder through the exhaust port View attachment 32149

And from the bottom of the cylinder up with less light View attachment 32150
Click to expand...
IT WIGGLES FROM SIDE TO SIDE FOR LUBRICATING PURPOSESo_O
THERE IS A TOLERANCE FOR IT HOWEVER
 
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DUALSTROKE said:
Well I still see some cross hatch in the bore, although it doesn't look like the best chamfer job. Tough to decipher from the pics. Look at all that meat on the sleeve. Perfect porting candidate!! And 1000 X's better than niche.
Click to expand...
And yeah man I was checking out the sleeve meat and she' pretty thick! Definitely good enough to still port/bore out and do a 240 kit. Was gonna send it to Ken but I've also been checking out CT Racings prices and they aren't really that expensive either :D
 
ProjectBlasturd said:
And yeah man I was checking out the sleeve meat and she' pretty thick! Definitely good enough to still port/bore out and do a 240 kit. Was gonna send it to Ken but I've also been checking out CT Racings prices and they aren't really that expensive either :D
Click to expand...
displacement has no contention on how a engine is tuned.........
lets see a yz125cc has 39hp stock
and a 200cc blaster has 16hp 17 18 19 whatever stock..........
the yz is 125cc blaster 200cc which has more power??
also i know the blaster weight's moreo_O
 
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