bored,ported and polished

hillbilly
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hillbilly
Edited Date/Time 9/10/2015 3:21pm
Local guy buys a bike online,2 actually,one in a box.

05 450crfs,he told me it was bored out and ported and polished,lol, Takes it straight to the track ,it was so clapped I wouldn't rode it to the gate.

After a bit it gets hard to start so he drops it by to get the valves adjusted. They were ok so I get him to put a piston in it.

After tear down I see a 93mm stamp on the piston,a one mil overbore,check the ring gap and it is not bad really.

I order a new 93 and gaskets,stick the piston on the rod and go toslip the cylinder over the rings and it just drops on.

Holy crap, measure the piston and it is a 93,then,I measure the cylinder. It is 94,2 mil overbore,lol.

Whoever had it before had put a 93mm in a 94mm hole with 94mm rings on it.

I've seen some crazy stuff but that one was up there, you would think it would made a lot of noise or vibs but it didn't.

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newmann
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newmann 9/9/2015 7:54am
9/9/2015 7:54am
Guess he wanted it set up "loose".Laughing Yikes....
hillbilly
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hillbilly 9/9/2015 8:10am
9/9/2015 8:10am
If I hadn't seen it I would not believe it possible to run any amount of time with the short piston skirts of these engines.

And the cylinder was fine,youd think it would been beat.
The Narrator 9/9/2015 8:14am
9/9/2015 8:14am
Ever get a guy tell you his motor is "borted"? A clever combination of bored and ported, I presume.
hillbilly
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hillbilly 9/9/2015 8:24am
9/9/2015 8:24am
The Narrator wrote:
Ever get a guy tell you his motor is "borted"? A clever combination of bored and ported, I presume.
You see my "milled head" post?

If no,I will type again,

Around here the quad guys will buy a new one and instantly mod it. The common one is milling the head like a v8.

But,sure you know ,when they stick it together it wont run rite and that is when they learn about moving the centerline of the cam and crank closer together which makes the cam timing late because the chain is not able to be shortened.

Now they get to buy a offset keys or a keyed cam.

The Shop

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Xeno
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Xeno 9/9/2015 8:40am
9/9/2015 8:40am
Use a cam sprocket with slotted bolt holes. Reset the cam timing.
The added compression will probably require race gas.
Hillbilly knows all this- I'm just "typing out loud" Laughing
The Narrator 9/9/2015 9:09am
9/9/2015 9:09am
The Narrator wrote:
Ever get a guy tell you his motor is "borted"? A clever combination of bored and ported, I presume.
hillbilly wrote:
You see my "milled head" post? If no,I will type again, Around here the quad guys will buy a new one and instantly mod it. The...
You see my "milled head" post?

If no,I will type again,

Around here the quad guys will buy a new one and instantly mod it. The common one is milling the head like a v8.

But,sure you know ,when they stick it together it wont run rite and that is when they learn about moving the centerline of the cam and crank closer together which makes the cam timing late because the chain is not able to be shortened.

Now they get to buy a offset keys or a keyed cam.
hand 'em a degree wheel and watch em thank you for the frisbee.
TXDirt
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TXDirt 9/9/2015 10:04am
9/9/2015 10:04am
was the power-band modded also? Tongue
HackMan162
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HackMan162 9/9/2015 10:36am
9/9/2015 10:36am
TXDirt wrote:
was the power-band modded also? Tongue
Some folk around these parts are dyeing their power bands. Pretty easy to go from red or blue to purple.
edgo897
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edgo897 9/9/2015 10:52am
9/9/2015 10:52am
You can raise compression by using a cereal box for base gasket material. Increase airflow to the motor by using a Scotch Brite pad for an air filter.
tunedlength
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tunedlength 9/9/2015 11:15am
9/9/2015 11:15am
The Narrator wrote:
Ever get a guy tell you his motor is "borted"? A clever combination of bored and ported, I presume.
Bortedished
neverwasfastenuf 9/9/2015 11:25am
9/9/2015 11:25am
hillbilly wrote:
Local guy buys a bike online,2 actually,one in a box. 05 450crfs,he told me it was bored out and ported and polished,lol, Takes it straight to...
Local guy buys a bike online,2 actually,one in a box.

05 450crfs,he told me it was bored out and ported and polished,lol, Takes it straight to the track ,it was so clapped I wouldn't rode it to the gate.

After a bit it gets hard to start so he drops it by to get the valves adjusted. They were ok so I get him to put a piston in it.

After tear down I see a 93mm stamp on the piston,a one mil overbore,check the ring gap and it is not bad really.

I order a new 93 and gaskets,stick the piston on the rod and go toslip the cylinder over the rings and it just drops on.

Holy crap, measure the piston and it is a 93,then,I measure the cylinder. It is 94,2 mil overbore,lol.

Whoever had it before had put a 93mm in a 94mm hole with 94mm rings on it.

I've seen some crazy stuff but that one was up there, you would think it would made a lot of noise or vibs but it didn't.

I thought those big four strokes lasted forever!
Andy_Greenney 9/9/2015 12:29pm
9/9/2015 12:29pm Edited Date/Time 9/9/2015 12:29pm
One of my first thoughts when riding a 450 is always....'I wish I had more power', lets have it bored out and ported
slipdog
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slipdog 9/9/2015 1:24pm
9/9/2015 1:24pm
Weirdest part is that the stock bore of a CRF450 is 96mm...
KMC440
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KMC440 9/9/2015 3:48pm
9/9/2015 3:48pm
HackMan162 wrote:
Some folk around these parts are dyeing their power bands. Pretty easy to go from red or blue to purple.
Best to walk away as they try to figure out what color to sdd to get to purple... lest you spend hours 'splanin roygbiv to them. Blink
MR. X
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MR. X 9/9/2015 4:38pm
9/9/2015 4:38pm
I like when people say they overbored their cylinder ,to me anything that is overbored has been bored to much.
Underground 9/9/2015 5:28pm
9/9/2015 5:28pm
Had an older 250 SX-F brought to me not running by a dirt poor kid. Got FA comp. Pull the head and see a fast from back then support riders name engraved on the side, porting that could have been done cleaner with a rat tale file and 2 nice round shiney spots on the exhaust side of std KTM piston with around 4mm of ring end. Couldn't believe the valves were still straight and lucky for him.

Funny how well that bike started and ran with 2 base gaskets and a new aftermarket std comp piston kit.
ns503
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ns503 9/9/2015 6:36pm
9/9/2015 6:36pm
edgo897 wrote:
You can raise compression by using a cereal box for base gasket material. Increase airflow to the motor by using a Scotch Brite pad for an...
You can raise compression by using a cereal box for base gasket material. Increase airflow to the motor by using a Scotch Brite pad for an air filter.
That actually works pretty good for keeping the snow dust out of your snowblower engine.

Pit Row

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Camp332
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Camp332 9/9/2015 6:54pm
9/9/2015 6:54pm
slipdog wrote:
Weirdest part is that the stock bore of a CRF450 is 96mm...
Everybody has to be drunk in this thread.
h&m_cycle
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h&m_cycle 9/9/2015 7:10pm
9/9/2015 7:10pm Edited Date/Time 9/9/2015 7:13pm
slipdog wrote:
Weirdest part is that the stock bore of a CRF450 is 96mm...
Camp332 wrote:
Everybody has to be drunk in this thread.
I had to read it 3 times... So stock bore is 96mm... The old piston was stamped 93mm & Hillbilly measured the
bore to 94.2? I knew too much Fox News would get him...

Jack_Wagon
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Jack_Wagon 9/10/2015 1:14am
9/10/2015 1:14am
93 is really 98? 94.2 is 98? Harbour Freight calipers accurate to +/- 3.8 mm.
imoto34
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imoto34 9/10/2015 3:53am
9/10/2015 3:53am
slipdog wrote:
Weirdest part is that the stock bore of a CRF450 is 96mm...
Camp332 wrote:
Everybody has to be drunk in this thread.
Silly
hillbilly
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hillbilly 9/10/2015 6:53am
9/10/2015 6:53am
slipdog wrote:
Weirdest part is that the stock bore of a CRF450 is 96mm...
Well,could be,I'm going off memory.

Point was it was 2mm over with a one mill over piston in it and 2 mill rings.

Another point is the thing stayed together for months,when you see one blown up think back to this then wonder just how youd have to treat one to get the rod outside the cases.
slipdog
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slipdog 9/10/2015 7:32am
9/10/2015 7:32am
slipdog wrote:
Weirdest part is that the stock bore of a CRF450 is 96mm...
hillbilly wrote:
Well,could be,I'm going off memory. Point was it was 2mm over with a one mill over piston in it and 2 mill rings. Another point is...
Well,could be,I'm going off memory.

Point was it was 2mm over with a one mill over piston in it and 2 mill rings.

Another point is the thing stayed together for months,when you see one blown up think back to this then wonder just how youd have to treat one to get the rod outside the cases.
Hahaha, I figured it was just "moonshine fingers". After a few I can't tell what letters are on the keys anuway, I jurt tri tu gst gjriegdc budiskjhxfjmc dda....
slipdog
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slipdog 9/10/2015 7:38am
9/10/2015 7:38am
19.5hrs on a full rebuild, cylinder kit was new. Athena says their part didn't fail, the piston seized and caused the cylinder to crack...










ktmdan
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ktmdan 9/10/2015 7:39am
9/10/2015 7:39am Edited Date/Time 9/10/2015 7:39am
Nothing funny about putting a 93mm piston in a 94mm hole, no one wins. Sad

edit: pun intended..
hillbilly
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hillbilly 9/10/2015 3:21pm
9/10/2015 3:21pm
slipdog wrote:
19.5hrs on a full rebuild, cylinder kit was new. Athena says their part didn't fail, the piston seized and caused the cylinder to crack... [img]https://p.vitalmx.com/photos/forums/2015/09/10/104550/s1200_Athena1.jpg[/img] [img]https://p.vitalmx.com/photos/forums/2015/09/10/104551/s1200_Athena2.jpg[/img]...
19.5hrs on a full rebuild, cylinder kit was new. Athena says their part didn't fail, the piston seized and caused the cylinder to crack...










That looks like oiling issue or cold seizure from tight tolerance or not warmed up enuff before putting it under heavy load.

Once the piston is scuffed it going to fail,could take it a while but it will fail.

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