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Big Bore Engine - Part 6 - Test & Tune (Read 363 times)
DragBikeMike
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #45 - 09/23/20 at 19:07:23
 
I don't think I have the skills to emboss fire rings into the copper gasket.  I know some guys machine o-ring grooves into the head and cylinder and the use stainless steel wire in those grooves.  The wire digs into the copper.  The problem with those approaches is some of the sealing wire or embossed area would not be circular.  The raised areas have to not only go around the bore but also the chain cavity, oil feed, and oil drain.  The stock gasket uses a fire ring around the entire perimeter of the gasket.

I have a bonafide granite plate that I used to lap both the head and the cylinder.  They're both pretty darned flat and smooth.  But the area along the chain case is just a tad low in relation to the majority of the sealing surface.  The copper gaskets may just not be forgiving enough to deal with the irregularities, especially if they are additive.  I intend to do a thorough check once it's all apart.  Maybe a skim cut or two.  But I am reluctant to use the copper again.  It's just too unforgiving.  

Dave, thanks very much for the temp data.  It helps a lot.  That area of the head obviously operates much cooler.  I suspect that's probably because it's adjacent to the intake port.  All the cooling from the fresh charge and fuel vaporizing pulls a lot of heat out of the area around the intake.  The spark plug is the recommended location for the CHT thermocouple, but the cavity is just too cramped.  With your data, we are starting to get a better idea of what to expect on the various regions of the head.
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Jdvt600
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #46 - 09/26/20 at 07:47:22
 
DragBikeMike

I just wanted to say thank you for posting this. This entire build has been fascinating to read. Your posts are inspirational to a newbie like myself.
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #47 - 09/27/20 at 19:02:02
 
A fantastic project, I predict by the time it's finished your LS650 will definitely be able to pull a fat kid across greased linoleum.
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #48 - 09/27/20 at 19:30:01
 
Mike,

When you get the engine out check the head torque too see if it changed.
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #49 - 09/28/20 at 14:46:29
 
eau de sauvage wrote on 09/27/20 at 19:02:02:
A fantastic project, I predict by the time it's finished your LS650 will definitely be able to pull a fat kid across greased linoleum.


That’s some funny $hit !  Grin Grin Grin
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DragBikeMike
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #50 - 01/16/21 at 17:01:10
 
Just wanted to fill you all in on the oil leak.  I was able to fix the leak by skim cutting the cylinder and cylinder head.

It helps to mark up your work piece with a felt-tip pen.  Then, when you kiss it with the tool bit you can see how exactly flat it is.
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #51 - 01/16/21 at 17:01:54
 
Just kiss the sealing surface with the tool bit.  The low spots will still have the felt pen marks.  Bingo, right at the pressurized oil passage.  It was barely .001” low but that solid copper gasket just couldn’t conform to the irregular surface.  Capillary action didn’t help either.
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #52 - 01/16/21 at 17:02:56
 
To mount the cylinder head in the lathe, I modified a torque plate.  The torque plate is fastened to the head with socket head cap screws, and then the torque plate is bolted to the head stock.  It’s a pretty simple setup.
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #53 - 01/16/21 at 17:03:41
 
More of the same with the cylinder.  Wouldn’t you know, the errors on the head and cylinder were in the same locations, so they stacked up.  It was destined for failure.  I won’t make that mistake again.  Note the copper strips between the acorn nuts and the cylinder bore.
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #54 - 01/16/21 at 17:04:18
 
The setup for the cylinder is more elaborate.  It’s a fixture with a machined fit for one end of the cylinder and an adjustable system for the other end.  You hold it with a 4-jaw chuck on the fixed side and a live center on the adjustable side.  Now you can adjust both ends to zero-out the workpiece.  You must use soft-rolled copper tubing between the adjusting nuts and the cylinder bore.  The adjusting nuts are aluminum acorn nuts, but I learned the hard way that they can still put a dimple in your workpiece.
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #55 - 01/16/21 at 17:05:01
 
Here you see the workpiece in the lathe.
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #56 - 01/16/21 at 17:07:21
 
Once the sealing surfaces were cleaned up, its was time to reassemble the engine.  I used Permatex Optimum Grey sealant again.  Since this final repair, I’ve logged about 650 miles on the 97mm engine.  It’s solid.  No leaks whatsoever.  Lesson learned, if you want to use a copper head gasket, the sealing surfaces must be perfectly flat.  The factory spec won’t work.  It must be flat within .000”.

While I was giving it a good shakedown, I tested some mufflers to see if I could squeeze out a little more power.   The LCGP muffler with 1.75” baffle tube worked well.  It pulled 4K to 7K in 5.72 seconds.  That was a nice improvement.  The Cherry Bomb brought the time down to 5.44 seconds.  It runs nice with that C-Bomb, but the noise is excruciating.

Both the LCGP and the C-Bomb wanted a lot more fuel.  For both mufflers, best performance was with a 240 main jet.  I didn’t have the benefit of the air fuel meter on the C-Bomb, but with the LCGP the 240 main jet yielded an A/F ratio of 12.1 to 12.5 at WOT.  The best acceleration times for both mufflers were with the 240 main jet.

Every chain has a weak link.  The weakest link on this project was the clutch.  Once I switched to the C-Bomb and dialed in the jetting, the clutch couldn’t hold the power.  It developed a slip in 5th gear.  I was on the freeway running about 4500 rpm.  There was no traffic.  You simply can’t resist the urge.  Once it hit about 5500 rpm at WOT, the tach took off.  The clutch just couldn’t hold the power.  It wasn’t gonna let me try and barge through a brick wall of air.

A quick inspection showed that all clutch components were like brand new.  All the discs met factory specs for a new clutch.  The spring load was the same as it was two years ago.  There was no discoloration or warpage.  So, it’s not worn out and it’s not burned up, it just can’t hold the power.

A Barnett clutch kit fixed the slipping.  I learned a few things on that project and am working on a report.  I will post that later.

The 97mm project was a complete success.  It’s a sweet powerplant.  Excellent manners, gobs of torque, blazing acceleration.

Now its time to move on to the next project.  I’ll start removing the 97mm in a few days so I can replace it with an engine that utilizes the 94mm Wiseco flat-top piston.  It will have significantly more compression and super-tight quench.  I can’t wait to see how the new engine stacks up against the Big Bore 97mm.
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #57 - 01/17/21 at 07:44:02
 
DragBikeMike wrote on 01/16/21 at 17:07:21:
The 97mm project was a complete success.  It’s a sweet powerplant.  Excellent manners, gobs of torque, blazing acceleration.

Now its time to move on to the next project.  I’ll start removing the 97mm in a few days so I can replace it with an engine that utilizes the 94mm Wiseco flat-top piston.  It will have significantly more compression and super-tight quench.  I can’t wait to see how the new engine stacks up against the Big Bore 97mm.


I'm not sure what Lances's supply looks like, but I'm very interested to see how the 94mm Wiseco stacks up against your 97mm.

I've got zero experience working on the internals of an engine. Although, I'm pretty sure with enough time I can git-r-done. I'm debating doing the 94mm in the garage myself, or trying to find a shop here in San Antonio that can bore it over and install the 97mm. I can't wait to hear about the torque, acceleration, and manners of the 94 Wiseco vs your custom 97mm.

Looking forward to your next project results!
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Re: Big Bore Engine - Part 6 - Test & Tune
Reply #58 - 01/18/21 at 03:46:46
 
Mike:

I am looking forward to your clutch modification.  My clutch is fine so far with my 95mm Wiseco and improvements - however there is very little extra strength in the clutch.  I have never used an oil with any kind of friction modifier or oil thickener (STP or Lucas).  I have the the Kevlar fiber plates and they work about the same as the stock plates - you have to make sure the clutch is completely engaged before you roll on the throttle.  If you try and grab a handful of throttle before the clutch is completely engaged it will slip.

I don't believe adding stronger springs is a solution - as the clutch throw out lever in the left side case is easily broken.  Even adding a washer under the springs has resulted in the throw out breaking - and a few people have broken that piece with all stock parts.  Machining a new throw out is a bit tough - as it has a "round with two flats" center hole that would require a broach to machine......I have considered the possibility of welding or brazing reinforcing metal on both sides of the throw out.

Badwolf has modified his clutch to eliminate the thin spring washer inside the outer plate.  His thought was that it resists some of the pressure applied by the 4 clutch springs.  He reports that he did not notice any change in the smoothness of the clutch after making the change.

I have been considering the idea of adding an extra friction plate.  If the fiber and steel plates were to be thinned down enough to allow an extra steel and fiber plate - there would be extra surface area after this change and the clutch would have more holding power.  It may be possible to machine away some of the clutch basket inside or outside face to provide more room.  MMRanch found that on his high mileage bike the soft wearing surface of the clutch had worn away a bit and his clutch was slipping - so he added an extra steel plate to take up the room and resolved his slipping problem.

If I have a thickness sander - thinning down the plates would be easy.  I am not sure if I could machine the plates on my lathe as they would be hard to hold, and the metal may be a bit too hard to machine well.  
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