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Nanno's "bumblebee" engine

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Nanno's "bumblebee" engine

PostAuthor: nanno » Wed Apr 08, 2020 6:13 am

... or the story of a poor little engine, which doesn't know it's not even meant to exist. :cl:

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The story starts with me being a bit unhappy about the engine, which I built lately. In essence, I've built the perfect race-engine, not much grunt down low, but oh-boy does it rev. (And make stupid power in the progress.) Unfortunately the specs said "everyday-engine" and it was rather bad at that compared to what I had before. So I inquired about combining the heavy crank with my BT/XVS/V-star rotating assembly and the universal answer was: don't. Prior to asking those questions, I had thrown some crude maths at it. (I will get into the intricacies of how and why this isn't very precise and you should do it differently in a subsequent post.) And worked out that the balance factor will go up, not realising that the new conrods have got lighter small-ends and that would limit the effects quite substantially.

stock XV1100
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XV1100 crank with (heavier) XV1100 conrods and BT1100 pistons
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XV1100 crank with light pistons and with the correct conrods as well
(The last calculation was done after I had the engine open and was able to extract crank and conrods.)
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And with that being said, I went through my stash of XV1100 cranks, dug out the one that was in the engine before and cleaned and stripped it.
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Pulling the engine apart revealed a nice surprise, the XV700 heads are working flawlessly with the tightened squishband as can be witnessed by the clean areas in the head where turbulence is happening.
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A quick check of the clearances between crank and conrod revealed Yamaha hadn't changed their tolerance codes and I made a spot on landing in the middle of the tolerance field with 0.040mm clearance, when combining BT-conrods with a XV1100 crankshaft.
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And there we have the unholy union, called bumblebee. Also my assembly lube is a bit stiff. :cl:
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Then followed the usual steps of reassembling the engine.
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Just to prove: These are actual BT-pistons
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Put the cylinders on
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No base gasket to improve squish, only rtv-silicone.
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And then after assembling the rest of the bike, I gave the exhaust a quick wipedown - the smoke in the video below is from the oil burning off.
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https://www.youtube.com/watch?v=Zdz8l_eMlBI

So what's it like: It's basically an XV1100 engine again, but with notably less vibrations. Actually hardly any vibrations at idle at all, which is almost a bit irritating. It has got low-down torque for miles and obviously it doesn't like to rev as hard or rev-up as fast as with the lighter BT crank. And incidentially it proved a point: a roughly 3 percent change in crank balance factor can be felt, if you compare them back to back. And also of course: bumblebees can fly. :cl:

(The full version is available on my blog under: https://greasygreg.blogspot.com/2020/04 ... lebee.html )
http://viragotechforum.com/viewtopic.php?f=12&t=43227 - Nanno's accumulated findings (and blatant show-off) - infos on my TR1's, my performance and reliability mods and a bit of show-casing of the stainless steel exhausts I build

*Look to my profile for a link to my blog*
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nanno
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Bike year & model: 1981 Yamaha TR1
1982 Yamaha TR1 Turbo
1977 XS 750 Sidecar
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1979 RD250/R5/DS7-hodgepodge (in bits)
Sex: Male

Re: Nanno's "bumblebee" engine

PostAuthor: faffi » Wed Apr 08, 2020 1:36 pm

So did you do the crank change before or after the universe told you not to? Anyway, happy for you that it worked so well :GJ:
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Re: Nanno's "bumblebee" engine

PostAuthor: nanno » Wed Apr 08, 2020 2:12 pm

After a lot of those "in the know" said it wouldn't work. Sometimes you gotta break some omeletts to make an egg (or something along these lines) :cl:
http://viragotechforum.com/viewtopic.php?f=12&t=43227 - Nanno's accumulated findings (and blatant show-off) - infos on my TR1's, my performance and reliability mods and a bit of show-casing of the stainless steel exhausts I build

*Look to my profile for a link to my blog*
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nanno
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Bike year & model: 1981 Yamaha TR1
1982 Yamaha TR1 Turbo
1977 XS 750 Sidecar
1984 XT500 4Valve (Austrian Tax saving edition)
1979 RD250/R5/DS7-hodgepodge (in bits)
Sex: Male

Re: Nanno's "bumblebee" engine

PostAuthor: faffi » Wed Apr 08, 2020 5:27 pm

I too tend to become more determined when people tell me it's a bad idea :bg:
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Current: 2001 XVS650 Drag Star Classic
Former: 1982 XV750SE with XV1100 engine and electrics, XT600Z shock absorber, 18" Seca rear wheel
Sex: Male

Re: Nanno's "bumblebee" engine

PostAuthor: Hellgate » Wed Apr 08, 2020 7:18 pm

I don't read well. [emoji6][emoji849]

Crank = BT1100
Rods = XV1100
Pistons = XV1100
Heads = XV700

Right?


BTW - I'd still like to buy your Nanno header system, seriously.
Pete
'12 Tuono V4R APRC
'05 R6 Track Bike
'88 RD350 YPVS
'82 XV920RJ
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Re: Nanno's "bumblebee" engine

PostAuthor: nanno » Thu Apr 09, 2020 6:15 am

faffi wrote:I too tend to become more determined when people tell me it's a bad idea :bg:


Hehehehe... To be fair some said it's a bad idea and others admitted, they've never tried. Then it was math's o clock and math's said it should work and produce less vibrations.

@Hellgate:

Almost, the setup is:

Crank: XV1100
Rods, Pistons, Cylinders: BT1100
Heads:XV700

Not hard to guess, I aim for maximum torque...

I am pretty sure we can work something out regarding an exhaust system for you. Maybe you would want to drop me a PM with your e-mail-address and we take it from there?

Cheers,
Greg
http://viragotechforum.com/viewtopic.php?f=12&t=43227 - Nanno's accumulated findings (and blatant show-off) - infos on my TR1's, my performance and reliability mods and a bit of show-casing of the stainless steel exhausts I build

*Look to my profile for a link to my blog*
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nanno
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Joined: Thu May 26, 2011 4:06 pm
  Flag
Bike year & model: 1981 Yamaha TR1
1982 Yamaha TR1 Turbo
1977 XS 750 Sidecar
1984 XT500 4Valve (Austrian Tax saving edition)
1979 RD250/R5/DS7-hodgepodge (in bits)
Sex: Male



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