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Author Topic: APS-PBG-650/750 build/change  (Read 10738 times)
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wobblywalrus
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« Reply #15 on: December 07, 2013, 12:40:22 AM »

Well setup engines do not blow head gaskets, one of my better tuning books says.  This is a big generalization, but there is some merit and a lot of truth to it.  Is the pressure spike from combustion occurring when the piston not far enough past top dead center?  Maybe the solution is to use a slower burning fuel or to retard the timing a little bit.
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JimL
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« Reply #16 on: December 07, 2013, 01:56:05 AM »

That can certainly be part of it.  I have had this happen with the timing retarded, also (slightly behind stock...back in the 34 degree range).  The kicker is that its usually (mostly) my forward cylinder on any of my engines.  My rear cylinder is mounted in a "taller" area of the block that is also carrying the trans cassette.  The pattern of failures is making me suspicious that I have pushed into some physics that Honda didn't plan for.

This could be an RPM related problem, also.  The Turbos dont seem to have a bigger problem than mine, but they are nearly 3000 RPM below the peak numbers I have been using (and I have been spinning these as much as 2500 over the original redline.)

Years ago, I was involved in head gasket investigations on a twin-cam V6.  The trouble turned out to be, in part, the need for "fast light" EFI tuning.  This is the various methods used to get heat into the cats as quickly as possible, to meet EPA standards for cold engine warm-up.

Drivers who were excessively gentle, during cold warm up, were accelerating gasket problems.  The slow rate of cylinder head expansion, overall, was not matching the growth of the exhaust side of the head (due to the need for late, long burn to blow heat into the cats).  The heads were bending sideways during a too slow, light load, warmup.  That stretched the ends of the gaskets far enough to tear the dowel pin holes open.  External water leaks were the result.

That issue is part of the reason all modern cars and trucks have stainless steel tubular or log headers (along with the need for less material to absorb heat that the cat needs for getting up to temperature).  The rest of the "fixes" remain proprietary information, but the manufacturers have all done good jobs of solving it, in various ways.

So...I'll bet component movement is some part of my problem.  What fails after I fix THAT, will be another mystery to ponder.

Hope you enjoyed the old history story on a cold, snowy night in the Oregon hills.  Yesterday morning I learned how far exploding Schedule 40 PVC water pipes can fly during the night (some pieces were 40 feet from the failure!). I guess I didnt get the above ground sprinkler system drained well enough.

JimL
« Last Edit: December 07, 2013, 02:02:20 AM by JimL » Logged
tauruck
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« Reply #17 on: December 07, 2013, 04:32:11 AM »

Jim, that's some very interesting information. Thanks.

I had some inch and three quarter metal pipes burst one day. It was -5*C in the house!!!!. South African farm houses are not built like yours.

Zero insulation.

 The pipes ran externally and I only knew there was a problem at lunch time when there was water gushing everywhere.
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Seldom Seen Slim
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« Reply #18 on: December 07, 2013, 10:08:39 AM »

Unh, Mr. Scrambler, sir -- are you sure about that thickness?  Isn't 25 mm about equal to 1 inch?  I'd say that'd make for some pretty low compression. evil evil
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Jon E. Wennerberg
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salt27
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« Reply #19 on: December 07, 2013, 11:20:58 AM »

Unh, Mr. Scrambler, sir -- are you sure about that thickness?  Isn't 25 mm about equal to 1 inch?  I'd say that'd make for some pretty low compression. evil evil


Someone is missing the point.   grin
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Seldom Seen Slim
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« Reply #20 on: December 07, 2013, 11:23:15 AM »

Speaking of someone -- Don, please accept our corngratulations on your son's accomplishment.  It's super-cool.  I'll let you decide to tell the group here, but whatever -- good going, Gus. cheers cheers cheers cheers
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Jon E. Wennerberg
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salt27
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« Reply #21 on: December 07, 2013, 01:42:41 PM »

Thank you Jon.

I will post in a LSR General Chat thread instead of hi-jacking Jims thread.

  Don
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SaltPeter
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« Reply #22 on: December 07, 2013, 05:32:30 PM »

Jim

Just some background about that Suby Mod.

From the discussions I had with the good people at Perfourmance, they had issues sealing the Heads in their 2.7 ltr Kit engines during the development stage, and found it was the Open Deck design of the 2.5 ltr Suby Block at the time (pre Turbo 2.5) causing the problems.

They looked at the factory Suby Turbo Engines 2Ltr and they had a Closed Deck, so they came up with their own modified "Big Block". It allowed them to run High Boost and develop 600 reliable HP at the crank.

Pete  cheers
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The Mission is to go as fast as possible along on that old Road Less Traveled.
JimL
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« Reply #23 on: December 07, 2013, 08:31:12 PM »

Thx.  I know open decks make cheaper casting processes.  I will fix this problem and we'll see if I can go a little faster...two runs in a row!

JimL
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JimL
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« Reply #24 on: December 10, 2013, 03:07:58 PM »

Just a "curiosity note" and a pic to show where this starts.  This picture was taken the first time we ever ran the bike un-streamlined.  You can see the room behind the engine, which will give me some space to move the engine back, if needed.  That could be required to make room for the blower in front of the crankcase. 

I'm hoping to gain a little left side weight with the intercooler, to prevent adding more left side ballast plates as seen in this photo.  There is also ballast on the countershaft cover.  If the batteries can move behind the engine, the blower might squeeze in front without moving the engine.  We'll know pretty soon.

Mainly, I want to keep plenty of weight on the front wheel.  Aerodynamic forces load the rear wheel just fine, for these small engine bikes.

JimL


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Freud
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« Reply #25 on: December 10, 2013, 05:31:04 PM »

Jim that's an excellent dark side foto.

FREUD
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JimL
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« Reply #26 on: December 10, 2013, 06:13:20 PM »

Yup, you are right about that dark side, sir!  A few people took pics because they'd not seen anything quite as homely.  Sometimes, things that work real well dont look very handsome.

(I keep trying to convince the lady, but she's not easily fooled.) cheesy

Hope to see you in February, and you stay warm and dry until our regularly scheduled winter returns.  I'm still on tire chains and 4wd up on this hill.

Regards, JimL

« Last Edit: December 10, 2013, 09:21:39 PM by JimL » Logged
wobblywalrus
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« Reply #27 on: December 10, 2013, 10:02:46 PM »

Jim, maybe you will not need to rev the bike as high with the blower and your gasket problems will be solved.

Jim, during the cold snaps you simply do not go anywhere.  Lots of fire wood, a warm wife, and a couple of bottles of hooch will keep you off the road until things warm up.  That is what we do here. 
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Old Scrambler
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« Reply #28 on: December 10, 2013, 10:12:34 PM »

Salt got the point...........I forgot it cheesy

Jim.......that is a fantastic build........all business.
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2011 AMA Record - 250cc M-PG TRIUMPH Tiger Cub - 82.5 mph
2013 AMA Record - 250cc MPS-PG TRIUMPH Tiger Cub - 88.7 mph
2016 AMA Record - 750cc M-CG HONDA CB750 sohc - 130.7 mph
2016 AMA Record - 750cc MPS-CG HONDA CB750 sohc - 137.7 mph
Chasis Builder / Tuner: Dave Murre
JimL
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« Reply #29 on: December 29, 2013, 10:56:03 PM »

Working out the supercharger drive from right end of crankshaft.  This stub will be machined to accept the drive pulley for the supercharger belt.  The stub has matching splines for the primary drive gear on the crankshaft.  The bolt shown is much longer than I will use, but it let me check run-out at the end of my drive stub, .001" is close enough for a multi-rib belt.

I will bore the hole in the clutch case (it is a threaded hole to access the orginal crank-shaft bolt).  With a sleeve over part of the splined shaft, I can fit a seal in the case.

I wish I would have thought of this connection point when I was trying to connect two engines.  I could have used a cog-belt and it would have been simple.

JimL


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