Wildguzzi.com
General Category => General Discussion => Topic started by: Barnapkin on September 19, 2025, 09:19:56 AM
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Hi,
Since the V85TT has a single TB vs one per cylinder, has anyone seen anything posted or tried boring the TB. If the TB were bored from 52 to 54. The same TB and manifold could be used. Almost comparing the area of the circle, 8% more air could flow. TB boring can be done for a few hundred dollars.
What am I missing?
Thanks for your review of this question.
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I guess it depends on what you're trying to accomplish.
If you've already increased flow at the airbox and exhaust, plus worked on the fuel map, then maybe over-boring the throttle body could increase power.
What have you already done with the bike, and do you have dyno testing results to map your progress?
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2022 model. I have full arrow exhaust, mistral velocity stack, k&n, and opened up the airbox holes. Stock closedloop keeps up so far. There are a couple dyno places but don’t know if they have software for the MG ECU.
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Don't know if its available in your area but there is a process called Extrude Hone whereby they flow an abrasive compound through the part and enlarge the interior to most any spec. Comes out rough or polished depending on your requirements. I have a friend who did baseline pulls on a small block GM stroker, Extrude honed the intake and heads for some enlargement but mostly to polish and match flow rates and gained 40 HP.
Might be worth looking into. My $.02
Paul B :boozing:
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Sounds like something to try on someone else’s bike first.
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Did you make mention of why you want to do it ?
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Did you make mention of why you want to do it ?
Ninja 250 syndrome?
When buyer purchases a lower HP bike and thinks that with a few simple mods, toggling on an electronic switch and/or drilling a hole in the air box the bike will instantly be uncorked and will instantly have the power and torque of a Moto GP bike.
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I am totally against modifying an engine unless you do the whole thing. When I was a kid I modified a Yamaha 80 so much it was quite quick for what it was. I think it lasted maybe a month before the bottom end went boom. New crank pin, rod and piston. When I built a Duster everything from the radiator to the rear end was upgraded to top of the line components.
kk
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As the old folks said, "If you need a motorcycle with more power, buy a motorcycle with more power."
Since buying my '21 V7 I've viewed a lot of vlogs and seen a bunch of "increase the power" products. Several, including some upMap info provide dyno charts and, if you believe them, show some gains of 3-5 HP. There is no way you are going to notice 3-5HP on the street, even if the gain actually exists. True, you might get some improvement to low speed fueling/smoothness which might be useful.
FWIW, I worked in high performance and competition engine building for years and the first principle re "performance mods" is: NEVER believe the claims of anyone trying to sell you something. OTOH if it is an objective dyno test by a disinterested party, that would be considered reliable.
I'll give two examples that I like from my engine-building days. A muffler company claimed their muffler added 13 HP over a stock 350 Chevy Camaro muffler and their ad provided the dyno chart to prove it. But although they weren't exactly lying, they weren't truthin' either. They compared their muffler to a clapped out, 10 year old OEM muffler and the dyno showed 13 more HP. That was not disclosed. Interestingly, later the shop then tested that straight-through (drop a golf ball through it) muffler and a NEW muffler from the Chevy parts department. The "performance" muffler was down by 7 HP over the standard muffler! I did the dyno tests...;)
I was at a NHRA event. One of the highly competitive pro stock teams between rounds was refreshing an engine and being filmed showing a well-known additive being poured into the engine oil filler. After the race I was talking to the crew chief that evening and I commented, "I didn't know you used [X additive]!" He replied, "We don't, what was in that bottle was [the normal engine oil they used] but [the additive] is one of our sponsors."
Let the buyer beware!!!
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I hope TN Mark doesn’t read this, he’ll want to fight you over such blasphemy!🤣
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Hi,
Since the V85TT has a single TB vs one per cylinder, has anyone seen anything posted or tried boring the TB. If the TB were bored from 52 to 54. The same TB and manifold could be used. Almost comparing the area of the circle, 8% more air could flow. TB boring can be done for a few hundred dollars.
What am I missing?
Thanks for your review of this question.
Is there even enough material to hog to make a difference?
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What am I missing?
Everything that’s important..
If you increased the amount of air thru’ the TB, that would send the mixture lean, the ECU would recognise this and add more fuel.
The brain has a target ratio of fuel/air mixture, why do (some) people become convinced that their engine is not getting enough air ?
You could satisfy the urge you have, by buying a 3” cube of machinable aluminium alloy, put a 1/2” hole thru’ it in a lathe, then bore the hole out to 1” and after doing that, put a boring bar thru’ and take it out to the size you want.
Then you could remove it from the machine, sweep up the mess on the floor and throw the block in the bin. The good side of all this, is that although you’d wasted one hour of your life, you’d still own a bike that runs nicely.
The only risk you’re running by leaving your bike alone is running the risk of boring your audience, not wrecking your lovely bike….
It’s an out there notion, but Piaggio and Moto Guzzi might have stumbled upon a nice result already, without your help…. :popcorn:
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Hi,
Since the V85TT has a single TB vs one per cylinder, has anyone seen anything posted or tried boring the TB. If the TB were bored from 52 to 54. The same TB and manifold could be used. Almost comparing the area of the circle, 8% more air could flow. TB boring can be done for a few hundred dollars.
What am I missing?
Thanks for your review of this question.
Any ideal what 8% more air flow could do for the bike?
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Depends on whether the ECU is capable of providing sufficient fuel to accommodate the additional air, AND whether the maximum benefit of the increase would occur within the current operating limits of the engine (redline) if both of those requirements are met, then you could figure around 6% increase in power at full throttle.
Re an earlier statement I made: "NEVER believe the claims of anyone trying to sell you something." Maybe I should have been less aggressive since that makes it sound like everybody that is selling something is misleading people and that is not correct. The problem is that you don't KNOW until you do some research OR you know the person/company you are dealing with and know you can rely on what they say. So, a better recommendation would probably be the old Ronald Reagan statement, "Trust but verify!"
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My experience in this realm is primarily with 2 strokes, so take it with a grain. Modding an EFI 4 stroke motor beyond simple air box/exhaust flow will have both consequences on your wallet and the reliability of the machine.
Other things to look at will be a reputable Dyno shop and fuel mapping for EACH mod you may choose.
High lift cams.
Winded crank.
Shaved heads.
Porting.
It all comes with benefits and problems. Much of these type of mods are necessary before intake boring becomes necessary (IMO)
If your intent is just to go fast....buy a croch rocket.
Oh, and also forgot...increasing airflow in a fuel/air chamber can cause unwanted turbulence or reduced/uneven fuel atomization due to a low pressure zone depending on where the injector is placed and how it was engineered.
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With the exception of Harleys, I have always felt that given the limitations of emissions and exhaust noise constraints, for most of the bikes that I have had, the engineers did their job and got nearly the most out of the bikes they can. Why would a manufacturer leave horsepower on the table?
My example is the BMW K1200 RS which I had made from 1998 - 2004. To get a 5 hp bump, you had to spend about $2,500 about 20 to 25 years ago (about $4,000 today). Also, many of the mods would change where the torque curve was, usually pushing it higher and except in those rare instances when you wanted to rev out, the general street drivability was actually worse. Most of our Euro bikes provide great midrange so the power is usable at our regular driving speeds, not high speed runs. Do you want to give that up?
The reason I mentioned Harleys is that due to their historic engineering, to comply with the regs, they had to leave quite a bit of horsepower out. So, as most know, on a twin cam 88, a real 10 hp improvement could be realized with an exhaust swap, new chip and airfilter mod. You could feel this difference. Of course, the bike was then technically not street legal after the mods so the exhaust said "not for street use" on them (wink, wink).
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Many years ago I had a friend who bought a new H1. He set it up with parts and tuning from a well known Kawi racer. It was the quickest thing I have ever ridden but it was a miserable bike to ride sensibly. It wouldn't idle below 2.5 K rpm, had no power down low. But wind it up, hang on tight and struggle to keep the front tire on the ground. It was fun to ride but I couldn't live with it.
kk
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Yeah, despite what most of us "performance-oriented" guys would like to accept. The manufacturers pretty much know what they're doing! :)
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Sometimes ONE change will result in a performance increase.
Many times that ONE change has to be allied with other changes.
For instance, I changed the exhaust cam timing on my KLR after reading an article about it and
reviewing the accompanying dyno charts. The resulting 10% (or so!) power increase
also required airbox mods. I had already modified the airbox, exhaust and
carburetor, so my engine was able to exploit the revised exhaust cam timing.
It pulls a higher top speed in top gear up hills and mountains now. There is
noticeably more mid-range power, which was what I wanted and what was
advertised. Not sure I would have realized that significant gain without ALL
of the mods.
Manufacturers have to balance engine longevity, driveability, noise regs, emissions
regs, maintenance hassles, and other factors when finalizing a design.That's
probably why Kawasaki sent it out the door the way they did.
The above mods result in a louder bike - one that isn't obnoxious, but certainly
wouldn't pass the government's tests. The cam change alone made things noticeably
noisier under heavy throttle. The carb mods probably won't allow the bike to pass emissions
standards, but markedly improve throttle response, and make the bike a whole lot
easier to ride. Fuel mileage appears unchanged after about 5,000 miles of testing.
Boring your throttle body with no other changes MIGHT improve your bike's powerband
and/or driveability. Might not. Your bike might need a bunch of other changes to take advantage
of the larger throttle body. Only one way to find out..... :evil: :laugh:
YMMV.
-Stretch
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Any ideal what 8% more air flow could do for the bike?
Just because the TB on its own flows 8% more doesn't mean that the entire system will flow any more mixture when running. It will only help if the TB is the bottleneck and then only at max HP. I suppose you could put it on a dyno and see what the pressure is in the intake manifold wide open at peak HP.
Looking around, I found dual 52mm TBs for auto engines making well over 200 HP so a single 52mm should be fine at 100, and the V85 isn't getting anywhere near that number. Also, apparently the BMW k1600 has a 52mm TB and makes 150+ HP. Also found someone with a 120 HP HD with a 55mm TB. Without looking further into it, I'd be surprised if the V85 made any more power with a bigger TB.