scarred cylinder

1584 Views 77 Replies 6 Participants Last post by TurboDave, 18 h ago

Jay.2515

Discussion Starter · 2 mo ago

So I pulled my head because while doing a spark splug change one of the valve cover bolts snapped.. no worries, I had a spare head laying around it was only when I seen that I have some wall scarring going on and it feels pretty deep in some places.. can I save it? Or do I need to go over size bore and if so what needs to happen?

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09_Blade

· #21 · 2 mo ago

Typical resurface grind is only 0.001 to 0.002". Last head I sent out for resurfacing only took off 0.001" to get the gasket surface perfect. That type of skim cut is not going to change compression, timing, etc.

HRC manual says gains are minimal, but can "improve airflow" by grinding down the valve guides. That is what the Millennium M-spec. CNC port offers, although I cannot imagine how that $1200 job could offer more than 2-3hp max. Better spend that money on some velocity stacks that offer +4-5hp for $400 if you really care about air flow, and even then it's only at high RPM's that you see the benefit.

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Jay.2515

Discussion Starter · #22 · 2 mo ago

09_Blade said:
Typical resurface grind is only 0.001 to 0.002". Last head I sent out for resurfacing only took off 0.001" to get the gasket surface perfect. That type of skim cut is not going to change compression, timing, etc.

HRC manual says gains are minimal, but can "improve airflow" by grinding down the valve guides. That is what the Millennium M-spec. CNC port offers, although I cannot imagine how that $1200 job could offer more than 2-3hp max. Better spend that money on some velocity stacks that offer +4-5hp for $400 if you really care about air flow, and even then it's only at high RPM's that you see the benefit.
[/QUOTE/] I think as far as skimming it down to the point where it’s changing the timing and compression is going to be too much for that. 2-3 hp gains are not worth it on this engine for that type of money in my opinion. Simply looking for a resurface to make sure I’ve got a good clean deck. I’m still not opposed to slapping a turbo on it and seeing some real power come out of this thing for the same amount of cash I’d spend to get 6-7hp haha. Got to make sure the engine is in top tier condition before that and it’s been the only thing holding me back.

DannoXYZ

· #23 · 2 mo ago

For any significant bumps in power, you want to go with TURBO!!

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Jay.2515

Discussion Starter · #24 · 2 mo ago

DannoXYZ said:
For any significant bumps in power, you want to go with TURBO!!

Turbo all day!!! I’ve gotta buddy who started working on me a plenum a few months ago. It’s been on pause for the moment because of all the issues. Hopefully by next year!!

TurboDave

· #25 · 1 mo ago

Jay.2515 said:
Turbo all day!!! I’ve gotta buddy who started working on me a plenum a few months ago. It’s been on pause for the moment because of all the issues. Hopefully by next year!!

I have a Cycle-Logics plenum, cold side pipe, and BOV for sale.

And It has already been said but I vote Millennium Tech as well. Don't even think about honing.

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Jay.2515

Discussion Starter · #26 · 1 mo ago

DannoXYZ said:
not worth it. These engines are extremely optimised from factory. You'll need to do complete hot-rod/racing build to get significant gains. Just slap in 12.5:1 pistons and get it tuned for 91 pump gas and call it good.

Lots of work to transfer everything to another case. Measuring for bearings, gaskets, etc. Easiest is just another used engine in good shape.

I was thinking and for future references about swapping cases.. would it be worth it to just swap the top half of the case and leave the original bottom half or would it still be too much of a pain in the ass with clearances.. mine is already out for millennium just wanted input on that considering I’ve never found anything other than people swapping entire cases.

09_Blade

· #27 · 1 mo ago (Edited)

Jay.2515 said:
I was thinking and for future references about swapping cases.. would it be worth it to just swap the top half of the case and leave the original bottom half or would it still be too much of a pain in the ass with clearances.. mine is already out for millennium just wanted input on that considering I’ve never found anything other than people swapping entire cases.

You CANNOT have mismatched upper and lower cases. It's due to the way the bore for the crankshaft bearings are machined with the two halves mated. Same for the camshaft holders in the cylinder head. You must replace both the upper and lower cases as a set to do a crankcase exchange.

In case anyone's curious, this is what a $1200 CNC port looks like with the valve guides ground down. There's very minimal material removed.

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Jay.2515

Discussion Starter · #28 · 1 mo ago

09_Blade said:
You CANNOT have mismatched upper and lower cases. It's due to the way the bore for the crankshaft bearings are machined with the two halves mated. Same for the camshaft holders in the cylinder head. You must replace both the upper and lower cases as a set to do a crankcase exchange.

In case anyone's curious, this is what a $1200 CNC port looks like with the valve guides ground down. There's very minimal material removed.

View attachment 267386

10/4, I guess that explains it all. Need to say no more. I’ve seen a lot of rebuild videos of people swapping entire cases and just throwing the good parts into the the cases without checking for clearances and these bikes are having no issues (on the video) lol. or are these people who are doing this just not going to see problems until later on? And what clearances should be accounted for when swapping?

09_Blade

· #29 · 1 mo ago

It's not just an issue of clearances, it's how the bearings are machined perfectly in line with each other. Imagine you take two blocks of wood and clamp them together, then drill a hole that intersects where the two pieces of wood meet. It's only a perfectly round circle for those two pieces of wood. If you try to do it again on a different pair of wood blocks and now swap the halves, it will approximate a circle but the hole will never be perfectly round.

Jay.2515

Discussion Starter · #30 · 1 mo ago

09_Blade said:
It's not just an issue of clearances, it's how the bearings are machined perfectly in line with each other. Imagine you take two blocks of wood and clamp them together, then drill a hole that intersects where the two pieces of wood meet. It's only a perfectly round circle for those two pieces of wood. If you try to do it again on a different pair of wood blocks and now swap the halves, it will approximate a circle but the hole will never be perfectly round.

Yes sir, I understand this completely. Is there a thread that shows people how to do this and what needs to be checked and how to check them properly and what needs to be done if clearances are off. I’ve checked and there’s nothing on it.

09_Blade

· #31 · 1 mo ago

It can be done manually with a bore gauge and micrometer, or you can go by the codes stamped on the crank and crankcase. There's a chart in the service manual that tells you what size (color) bearing to order, and you double check with Plasti-gauge for each bearing.

DannoXYZ

· #32 · 1 mo ago (Edited)

Jay.2515 said:
10/4, I guess that explains it all. Need to say no more. I’ve seen a lot of rebuild videos of people swapping entire cases and just throwing the good parts into the the cases without checking for clearances and these bikes are having no issues (on the video) lol. or are these people who are doing this just not going to see problems until later on? And what clearances should be accounted for when swapping?

Are they splitting cases and mixing and matching? That'll never work. You gotta take all of it. Then swap crank, rods & pistons across. This is where you have to start measuring clearances.

TurboDave

· #33 · 1 mo ago

If reusing the cases and crank, check your old bearing to see what color code they were and make a note of it. Three of mine out of a stock motor didn't match the bearing recommendation on the chart. I think the chart shows the first bearing to try, and the final required bearing is determined by the plasti-gauge method.

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Jay.2515

Discussion Starter · #34 · 1 mo ago

Okay so replating is unfortunately off the table now. They’ve found more issues and it’s basically scrap metal. On another note I have found a good casing and I went ahead and picked it up for 485.00.
Oem piston set are around the same amount as a set of forged. I would like to go forged but My problem is I read JE pistons will eat up my cylinders walls if you don’t get a replate and if I just hone then I need to use oem rings with the JE. Any one have any input on the route i need to go if I wanna go forged?

09_Blade

· #35 · 1 mo ago

A set of used stock pistons (check skirts), new stock rings, and a deglaze of the bore is the cheapest way to do it.

Is the reason for forged only to achieve a higher compression ratio? Gains are minimal and I'm not sure I understand your rationale for forged pistons when you are running stock bore, crank/cams, etc.

Jay.2515

Discussion Starter · #36 · 1 mo ago

09_Blade said:
A set of used stock pistons (check skirts), new stock rings, and a deglaze of the bore is the cheapest way to do it.

Is the reason for forged only to achieve a higher compression ratio? Gains are minimal and I'm not sure I understand your rationale for forged pistons when you are running stock bore, crank/cams, etc.

By chance would you know what I’d need to hone this motor with?? I’ve read that a honing ball is too abrasive for these motors and it would take too much material off?

The only real reason for forged bottom end was for the purpose of beefing up the bottom end if I ended up wanting to run boost in the future.

09_Blade

· #37 · 1 mo ago

It's more of a deglazing procedure done with a Flex-hone tool in a power drill. You want to create a light cross-hatch pattern in the cylinder walls.

If you want to beef up the bottom end, you need to run aftermarket connecting rods and wrist pins.

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Jay.2515

Discussion Starter · #38 · 1 mo ago

09_Blade said:
It's more of a deglazing procedure done with a Flex-hone tool in a power drill. You want to create a light cross-hatch pattern in the cylinder walls.

If you want to beef up the bottom end, you need to run aftermarket connecting rods and wrist pins.
[/QUOTE
There’s one guy on here who say to use nothing more than a red scotch brite and people swear by this guy. I’ll check out the hone tool as well if you have a link to a specific one and the type of oil that needs to be used. That would be greatly appreciated!!!

DannoXYZ

· #39 · 1 mo ago (Edited)

Jay.2515 said:
Okay so replating is unfortunately off the table now. They’ve found more issues and it’s basically scrap metal. On another note I have found a good casing and I went ahead and picked it up for 485.00.
Oem piston set are around the same amount as a set of forged. I would like to go forged but My problem is I read JE pistons will eat up my cylinders walls if you don’t get a replate and if I just hone then I need to use oem rings with the JE. Any one have any input on the route i need to go if I wanna go forged?

Forged pistons only needed for high-compression or boosted applications. Modern cast hypereutetic pistons are extremely tough. Rings have to be compatible with nikasil coating. Same with pistons, typically an iron-coating is used on pistons for alloy bores (Porsche & BMW). Personally I wouldn't use JE pistons. Wosner is my go-to.

To reduce compatibility issues, go with new OEM pistons and rings. Bores should be re-plated, not sure there's enough thickness to hone. Again, you need to measure everything 1st in order to come up with plan. Most likely piston-to-cylinder clearances on replacement cases are on large side due to wear & tear. So you'll need to re-plate cylinders to get clearances back to factory OEM levels. Send everything to Millenium and have them measure and make an assessment.

Never buy pre-gapped rings! They are typically gapped too-large and pre-worn for people doing just what you're doing without measuring. So they're gapped on large end, so you're buying pre-worn rings! I only get un-gapped rings and I'll gap myself to minimum OEM spec, then pull them after couple 100-miles and re-measure gap. Then grind another set with tighter clearances then repeat. Typically take 3-5 rounds until I see fretting marks at ends of rings. Then I put previous set back in.

Remember, you are doing all this work to create a stock motor with stock performance.

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TurboDave

· #40 · 1 mo ago (Edited)

Jay.2515 said:
By chance would you know what I’d need to hone this motor with?? I’ve read that a honing ball is too abrasive for these motors and it would take too much material off?

The only real reason for forged bottom end was for the purpose of beefing up the bottom end if I ended up wanting to run boost in the future.

I "deglazed" and cross hatched my scored nikasil cylinder once with a 3" 400 grit Aluminum oxide ball hone and oil. I tried to do as little as required to clean up the scoring. I suspected this was one of a few mistakes that led to engine failure. I got pits in the wall from the rings which eventually cracked them. This was mostly due to a bad tuning on the dyno but I always wondered if I weakened the cylinder walls by overdoing the honing. Now, I just have it plated for insurance. What did Millennium find that they cant repair? The damage shown below came back from Millenium looking better than new.

The type of piston for turbo isn't as critical as a good tune. The stock pistons are forged and can handle some abuse. They held up under 10-15 psi boost for many years before I pulled them to build a high boost motor. My JE low compression turbo pistons used in the scenario above blew after a few minutes on the dyno. The most important thing is the tune.

Any motor built to be turbo'd in the future would have to be stock compression or lower. I'd just build the n/a motor the way you think best and plan to build a turbo motor later.

I'd use new oem piston rings.

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