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Author Topic: One for the 250cc folk  (Read 40593 times)
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edinlr
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« Reply #180 on: October 02, 2015, 12:47:02 PM »

If you are having gear drive issues, then I think option #5 is your only way to go.  Otherwise you need to calculate your compression with the thicker head gasket and try to determine if cleaning up the piston or the head may help preserve some compression.  After all the hard work you don't want to go and lose a couple points of compression if you can avoid it.  It looks like with the interference on the piston being on the sides under the pin, that you should have plenty of material to take off a touch to help your clearances.  I have done tons of pistons by hand in the old days, but I would probably have someone mill off the material to be more precise.  You also should contact your piston supplier to see what they say too.  Last, with those floating cylinders, I am guessing you will always have problems getting a good seal especially with the rpm you pull.  I am thinking JimL used to try to get 3 or 4 runs between having to replace gaskets on his CX race bike.
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Honda CX650 turbo
generatorshovel
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« Reply #181 on: October 02, 2015, 03:29:52 PM »

If you are having gear drive issues, then I think option #5 is your only way to go.  Otherwise you need to calculate your compression with the thicker head gasket and try to determine if cleaning up the piston or the head may help preserve some compression.  After all the hard work you don't want to go and lose a couple points of compression if you can avoid it.  It looks like with the interference on the piston being on the sides under the pin, that you should have plenty of material to take off a touch to help your clearances.  I have done tons of pistons by hand in the old days, but I would probably have someone mill off the material to be more precise.  You also should contact your piston supplier to see what they say too.  Last, with those floating cylinders, I am guessing you will always have problems getting a good seal especially with the rpm you pull.  I am thinking JimL used to try to get 3 or 4 runs between having to replace gaskets on his CX race bike.
The gear clearance is only a problem after skimming the head, compression point losses are advantageous, given the engine is supercharged, these pistons have had the crown peaks removed  and the peaks are now @ the level of the original spark plug indents.
If you want to upset piston suppliers, just ask them to forge 49.5mm custom pistons, they don't really want to know, and price accordingly , the cheapest quote was $500 each, bare !
The copper gasket that is being used up until now has survived 2 engine disasters, 2 official runs, & over 50 hard miles with no leakage, all with between 10 & 15 LB boost.
There is no easy way to modify these ladies wrist watches, that Ive found (yet)
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Tiny (in OZ)
I would prefer to make horsepower, rather than buy, or hya it, regardless of the difficulties involved , as it would then be MINE
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« Reply #182 on: October 02, 2015, 03:51:03 PM »

Option 5 is my choice,
 A 2 mm head gasket will give me .0354" clearance (same as with head #1) which is more than enough to allow for rod stretch / crank flex past the operating rpm
I may have to remove some alloy beneath the 3rd cam gear and shim the cassette to suit , this is also a PITTA as the gear is a "scissor" split type , spring loaded,(to quieten the gear train), this makes measuring the gear fit difficult, but if I spread the "scissor" gear to line up the teeth, clamp it, then measure the lash I should be ok ?

Man I HATE it when there is no way to "adjust" the lash in gear drives.    Lack of adjustments requires VERY tight tolerances for the parts.

What the factory is really doing is:  Making the parts throwaways when they are "out of spec".   Expensive.   And when the design is no longer serviced for replacement parts, well . . . . . . . . .

You are right.  Option 5 is the only choice.

 cheers
Fordboy
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generatorshovel
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« Reply #183 on: January 05, 2016, 11:46:48 PM »





Are we there yet ?  grin
« Last Edit: January 05, 2016, 11:48:36 PM by generatorshovel » Logged

Tiny (in OZ)
I would prefer to make horsepower, rather than buy, or hya it, regardless of the difficulties involved , as it would then be MINE
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« Reply #184 on: January 06, 2016, 04:47:33 AM »

Nice.

Your shed (?) looks kinda like my garage.

I presume you are off to the lake this year.    Best of luck to your efforts.

 cheers cheers cheers
Fordboy
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I used to be a people person.  But people changed that relationship.

"There is nothing permanent except change."    Heraclitus

"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."     Albert Einstein
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« Reply #185 on: January 06, 2016, 04:34:37 PM »

Nice.

Your shed (?) looks kinda like my garage.

I presume you are off to the lake this year.    Best of luck to your efforts.

 cheers cheers cheers
Fordboy
I have history, working myself into a different corner of the shed  smiley each year, this is the 1st tine I've been close to the kitchen sink.
I hope you are as good at cleanup as you are with engines Fordboy ?
 I still rent space in forwards backwards land apparently, I managed to drop a 4mm grub screw into the blower (retrieved) , neglected to disassemble the Holley needle & seat assembly on the Mikuni fuel carb mods , it flooded, sneakingly, which was the reason for the difficult starts, then,,the salt got into another grub screw in the blower drive extension shaft  , when is tight, not tight in the right places ?,,when the top belt pulley & shaft try to part company from the blower (luckily the cover was off,  I wasn't riding, & it was idling, so I had time to kill it before any damage was done),,that's today's job .
 Runnin' outa time,,,,,,,,,,,,, shocked
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Tiny (in OZ)
I would prefer to make horsepower, rather than buy, or hya it, regardless of the difficulties involved , as it would then be MINE
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« Reply #186 on: January 07, 2016, 09:32:56 PM »

Tiny, this is extremely Mickey Mouse, but it works...sometimes.  The method is to put bluing dye on your gears and to see exactly where they interference occurs.  You are lucky sometimes and it is at the tip of the teeth where they fit in the valley of the other gear's teeth.  In this case, the offending male gear can be put in a lathe and the tops of the teeth skimmed off just enough to get a clearance fit.  Keep in mind that the aluminum engine parts that support the gear train expand more with heat than the gears.  The gear-to-gear clearance will increase when the engine heats up, so being a bit tight when cold might not be as big of an issue as one thinks.  Another Mickey Mouse solution is to make a 50-50 mix of Comet or Bon-Ami and grease and to use this to lap in the offending gears.  Sometimes this is all that is needed to do the job.  The hardening layer on Honda gears is sorta minimally thin so this method should not be used to remove more than a few thousandths of an inch at most.   
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« Reply #187 on: January 08, 2016, 12:02:05 AM »

Thanks Bo,,Iv'e been a bit busy lately, I should have posted a followup regarding my clearance issues,,
  I found the problem, ME !
Under (almost) every head bolt, there is a copper washer,,,what I neglected to remember was that the bolt directly under the gear cassette does not use a copper washer,
To really throw me, one tooth on the idler gear is 3 poofteenths higher than the rest (who says Japan make quality stuff?), and it just happened to nudge the head bolt @ TDC, Once I removed the washer, like the good book said (in Japanese) , problem solved  rolleyes
I now have a spare 1.6mm copper head gasket, so I can not worry too much about skimming the head next time  cheesy
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Tiny (in OZ)
I would prefer to make horsepower, rather than buy, or hya it, regardless of the difficulties involved , as it would then be MINE
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« Reply #188 on: January 08, 2016, 07:33:20 AM »

Nice.

Your shed (?) looks kinda like my garage.

I presume you are off to the lake this year.    Best of luck to your efforts.

 cheers cheers cheers
Fordboy

I hope you are as good at cleanup as you are with engines Fordboy ?


Ahhh, sort of.    The wife's car still won't fit in the workshop (she still insists it is HER garage . . . . . .) so that's a bi-annual "issue".     Can't complain too much though, overall she is a keeper.

 cheers
F/B
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Seldom Seen Slim
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« Reply #189 on: January 08, 2016, 08:08:22 AM »

Tiny said:  "...one tooth on the idler gear is 3 poofteenths higher than the rest..."

Poofteenth?  Good word.  Must be from your neck of the woods -- haven't heard that one before.  Now - if you'd said that it was "3 RCHs proud..."  I woulda knowed whatcher sayin'.
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Jon E. Wennerberg
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« Reply #190 on: January 08, 2016, 08:30:13 AM »

RCH?
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John Gowetski, red hat @ 221.183 MPH MSA Lakester, Bockscar #1000 60 ci normally aspirated w/N20
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« Reply #191 on: January 08, 2016, 08:38:01 AM »

Aw, c'mon, Johnboy.  You're telling me that you've never heard of that very small yet precise measurement?  Nah, I don' believe it. grin
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jacksoni
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« Reply #192 on: January 08, 2016, 08:49:56 AM »

Aw, c'mon, Johnboy.  You're telling me that you've never heard of that very small yet precise measurement?  Nah, I don' believe it. grin
And then there is the even smaller precise measurement- a flat one...... cheers
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« Reply #193 on: January 08, 2016, 11:53:57 AM »

A red one grin Just wanted to see what you would say. I had to explane that to a female captain when I was in the Air Force. The colonal was surprized when I told her it was a unit of radar measurement.
« Last Edit: January 08, 2016, 12:00:37 PM by Speed Limit 1000 » Logged

John Gowetski, red hat @ 221.183 MPH MSA Lakester, Bockscar #1000 60 ci normally aspirated w/N20
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« Reply #194 on: January 13, 2016, 06:03:59 AM »

One of my (very) old timers is "foreskin of a fly's di*k- just a whisker.
Denis
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