Topic: CB550 Top End Rebuild

[dave500]

just use the 1st oversize,run the stock airbox and itll haul arse the same as wasting money on all that other #$%*,your not gonna turn it into a fire breathing monster with that crap,#$%* I can run late model bikes into the weeds in the twisties over and over again,few threads on poor cruising image piston kits on this forum?ive thrashed the david silvers one with no mercy for a few years and it holds fine.

[calj737]

Personally, I like the Wiseco 59mm forged pistons. They will bump the CR, won’t cost an arm and a leg for boring, and are top quality. You will have ample cylinder wall left too. Mikes work on yuor head will unleash plenty of ponies, and the added CR and 650 cam will wake your bike up nicely.

Skip the CruzinImage pistons. They’re “OK”, but you won’t see nearly the results for the same amount of displacement changes as they lower the CR.

[Stev-o]

+1 on the forged Wiseco's, I have them in a couple of my bikes.

BTW - my machinist charges $50/hole for boring [just to give you an idea of cost]

[CJK]

Personally, I like the Wiseco 59mm forged pistons. They will bump the CR, won’t cost an arm and a leg for boring, and are top quality. You will have ample cylinder wall left too. Mikes work on yuor head will unleash plenty of ponies, and the added CR and 650 cam will wake your bike up nicely.

Skip the CruzinImage pistons. They’re “OK”, but you won’t see nearly the results for the same amount of displacement changes as they lower the CR.

Cool, I’ll just do it. You haven’t steered me wrong, yet and it makes my wallet lighter

Stev-O -- Thanks for the cost estimate. I'm sure the cost will be more here, but I shouldn't expect to pay >$100/cylinder for a +0.5mm bore and alignment. I know machinists are professionals that do this work, but is there anything I'll need specify?

My thoughts are to order the pistons first.
Upon receiving the pistons, have the cylinders bored out and matched to the pistons // Cylinders decked flat
Install pistons + rings, MLS head gasket, trim dowels if needed.

Is $135/piston set ($540 total) about the price to pay?
Should the thickness of the MLS head gasket match the amount removed from top of cylinders and bottom of head?





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[calj737]

Take the pistons and rings and the block to the machinist. The pistons have a declared wall-piston clearance. The machinist will bore each cylinder to the exact diameter needed per piston, labeling each piston (Wiseco’s rally won’t vary  ). The rings will be checked for end gap.

Block decked, choose a gasket (confer with Mike) or appropriate thickness for best CR and valve/piston clearance. You often have a fair bit of “room” between the top of the piston at TDC and the block deck (maybe as much as 0.040 in some cases). Milling the block down to get a final clearance squish nearer to 0.032 (with gasket compressed) is about optimum. You don’t need to chase that clearance, just be aware of it. Heck, 0.050 works just fine...

Your shop will be in the $40-$75 per hole. At 0.5mm bore, it really should not be expensive.

[dave500]

itll be better than new then and last  forever,dont baby the break in!just start riding it hard,coupla short oil and filter changes,then itll be normal.

[CJK]

Take the pistons and rings and the block to the machinist. The pistons have a declared wall-piston clearance. The machinist will bore each cylinder to the exact diameter needed per piston, labeling each piston (Wiseco’s rally won’t vary  ). The rings will be checked for end gap.

Block decked, choose a gasket (confer with Mike) or appropriate thickness for best CR and valve/piston clearance. You often have a fair bit of “room” between the top of the piston at TDC and the block deck (maybe as much as 0.040 in some cases). Milling the block down to get a final clearance squish nearer to 0.032 (with gasket compressed) is about optimum. You don’t need to chase that clearance, just be aware of it. Heck, 0.050 works just fine...

Your shop will be in the $40-$75 per hole. At 0.5mm bore, it really should not be expensive.

Thanks for the walkthrough, Cal. Now I feel like I understand how to go about this.

Update:
- Head and intake runners en route to Mike

- 59mm Pistons kits will be purchased this weekend

- I called a couple machine shops around me and they quoted me $50-60/hole for boring

- I discovered that my employee has a hardly used but very well-funded small machine shop that we have access to after a couple classes. I signed up and pretty soon I’ll have access to mill and lathe + other metal working machines.

- while I’m waiting for the engine work, I’ll work on cleaning the carbs to make sure they are pristine inside.



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[CJK]

Update here!

- Mike is finishing up the work on the head this week. It was essentially a stage 3 port job with new valves, spring, guides, seals, and modified to fit larger cam.
- Cylinders are bored to fit pistons and pending measurement from me to deck from top.
- Carbs are disassembled and need to be finished cleaning + reassemble


Question:
Mike said the head had 0.004" material removed when it was milled flat. How much should be decked from the top of the cylinders?

MLS gaskets are available in 59mm x 0.040" and 0.050".

[calj737]

Question:
Mike said the head had 0.004" material removed when it was milled flat. How much should be decked from the top of the cylinders?

MLS gaskets are available in 59mm x 0.040" and 0.050".

It all depends. How deep are the pistons sitting below the deck when assembled? How tight a squish band do you seek? I used the 0.040 with a final squish to 0.032, but I had the deck milled until the pistons were sitting just about dead flush (they were 0.032 in the hole). Don’t forget if you mill the deck, the locating dowels need to be trimmed else they will suspend the head.

[CJK]

It all depends. How deep are the pistons sitting below the deck when assembled? How tight a squish band do you seek? I used the 0.040 with a final squish to 0.032, but I had the deck milled until the pistons were sitting just about dead flush (they were 0.032 in the hole). Don’t forget if you mill the deck, the locating dowels need to be trimmed else they will suspend the head.

Cal,

I haven't assembled it yet. So if my understanding is correct, the critical measurement is the piston TDC to chamber because that affects both clearance but also the volume of the combustion chamber? What is the actual measurement that I'm trying to solve for?

Since I know 0.004" was removed from the head, the variables that I can alter to end up with the proper measurement are:
- head gasket thickness (course adjustment 0.030", 0.040", and 0.050")
- amount of material removed to deck cylinders


Process:
1) Re-assembled cylinders with pistons
2) Measure height of pistons in cylinders at TDC


Should I be concerned with using a new, uncompressed base gasket between cylinders and case?

[calj737]

Assemble the pistons inside the block. Measure across the top plane to top of piston. Calculate your gasket thickness by subtracting the compression of the gasket from the total thickness, then the depth of the piston. You can get about 0.008 with HD studs.

[CJK]

Head arrived back from MReick completely rebuilt and what he called a “Stage 2.5” job.

Ring end gap measured and set as per Wiseco Specs. Pistons assembled back in the cylinders and connected to rods.

Next, I need to measure across the top of the pistons to determine gasket thickness.

The pictures below are with the pistons at TDC.

I did an initial measurement but what it was getting late so I was rushed.

Where should I be measuring the piston? At the center or the edge?

Is my measurement method correct or should I be using a flat ruler across the top and a feeler gauge?







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[calj737]

That’s pretty close. A 0.040 gasket should be ample clearance depending upon the camshaft you’re running.

You might be well-served to do a bit of research on “engine clay clearance” to understand how to get the actual piston-valve clearance required for your engine. Nothing will suck more than to assemble it, whack it, then discovering those valves are clanking into your Wiseco slugs  This is the stage where 0.000s matter a LOT.

[CJK]

I’ll be running a CB650 Camshaft, which from my memory provides increased duration but no additional lift.

I think the engine clay clearance is a solid idea. I’ve already invested enough time and money to do it right, might as well continue on the path rather than shortcut and risk damage.

[calj737]

Mine were sitting 0.032 short of the deck. But due to the cam I chose (MegaCycle 126-20) some clearance milling in the piston was required.

[CJK]

That would make sense why I’m measuring about -0.010” from yours (assuming you haven’t had any material decked).

Head -0.004”
Cylinders -0.005” (by Recollection)

I just watched a YouTube video on the clay method. I’ll order both 0.040” and 0.050” MLS gaskets. Does any company make spacers that are are like 0.005” (to use as like shims)?

EDIT:

It seems only Dynoman has 0.040” and 0.060” thickness 59/60mm gaskets.

[calj737]

For the record, I had my deck milled to move the pistons all the way up (removing the 0.032 essentially). My head was milled 0.006, which I also removed form the dowel pins. I then used an 0.040 gasket with HD studs, and final squish resulted in 0.032 (0.008 coming out of the stud torque). Thats a very tight and healthy squish.

With yours already 0.02x deep, a stock 0.040 gasket will be plenty of clearance with a 650 cam and stock sized valves (I used +1mm oversized intakes). Don't order a gasket until you determine your final depth, then get it through Mike. Don't forget the base gasket thickness too. 

[CJK]

I did install the base gasket supplied with the Vesrah kit, but have not yet put the head on or torqued anything down. I used a dead blow mallet to gently pound down the head to seat it.

Thinking about it, when talking about thousandths, that could affect the measurements.


I’m a little confused as to your last comment for next steps, you would recommend ordering a 0.040” MLS Head Gasket?

Or I should assemble head (without a HG) and torque to spec to squish/seat the cylinders/head, remove head, then measure for final depth?

By the way, the MotoGP pipe will sound and work well once it’s all back together!


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[calj737]

I suspect an 0.040 will be just fine unless you mill the block more (unnecessary). Torque everything down with clay on top of pistons. Rotate the cam to get your clearance. Remove head. Then you’ll know which gasket to get.

[CJK]

I suspect an 0.040 will be just fine unless you mill the block more (unnecessary). Torque everything down with clay on top of pistons. Rotate the cam to get your clearance. Remove head. Then you’ll know which gasket to get.

Roger, will do it on Saturday! Thanks Cal.

[dave500]

I put xl125 pistons into a cb500 once,the xl are domed,gotta check clearance,standard cam on this motor was fine,my 550 still hauls better than this did with flat tops!

[CJK]

Ok, one step forward, and I’m stalled again.

Cylinders, cam chain tensioner installed. Then I installed the head on top of cylinders with dowel pins but no HG. The pins won’t need to be trimmed at all as the head and cylinders mated together perfectly.

After that, I torqued the head down to spec (after using tap and die to clean stud and nut threads). Then installed CB550 cam with the CB550 Cam sprocket.

To ensure I didn’t bend any valves, I backed the  rocker arm tappets all the way out as well as used the rubber band trick to hold the rocker arms up.

The problem I am running into is when I place the valve cover on, whichever lob is at TDC is pushing the cam shaft all the way down to the valve stem. In order to torque the valve cover down, I would have to keep tension on the valve stem and there would be 0 tappet clearance




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[bryanj]

There will always be valve(s) that are open at any point of engine rotation, as long as the adjusters are not pushing the top of the valve stem sideways you are good to go.

[calj737]

You can rotate the crank until no cylinder is at TDC, but the valve cover torque is only about 10 ft/lbs.

[CJK]

Thanks Bryan and Cal, I’ll give it a try right now


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