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Need Advice with Mystery VTR mods

Old 02-02-2019, 08:47 AM
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Need Advice with Mystery VTR mods

Hey all, lurked a long time, had a Superhawk many years ago and countless RC51's. I got another Superhawk from a friend a couple years ago. It got pushed to the back of the pile, then was waiting on paintwork and now finally I am bringing it back to life.

It came from Reno, and has gone through two friends, but the supposed history on it was that the engine was built by Bob Hyashida or at least has some Mori parts installed, and both buddies said it feels way to fast for a stock S-hawk.

Bike has obviously been well looked after and it appears that the cases have been apart. Aside from that it is safety wired everywhere but too clean for a race bike. It also has other curious mods like a bung welded to the left side of the frame for a damper that could pass for factory Honda it is so nice.

Bike has a full Moriwaki exhaust and I tore into carbs yesterday and this is what is interesting. The TPS is unplugged and the wire going to TPS is neatly tucked away and zip tied, so looks like it was not an after thought.

Carbs have what I believe is HRC kit, single hole lift slides, needles on 3rd clip down from top, 175F and 178R, 50s pilots.

I do not believe it has HRC cdi as bike will die in gear with kickstand down.

Got everything cleaned up and back together, starts up and runs fine but some popping and small flames out of the exhaust after revving (have not ridden yet).

I intend to dyno the bike to see what kind of power it makes and I think that would determine if it has cams or pistons etc...no porting work on heads that I can see.

So main question is after all that...ANY reason at all TPS would be or should stay unplugged? Was there any race/track setup back in the day that did away with it?
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Old 02-02-2019, 10:40 AM
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Is said bike blue with a RC51 front end? May belong to a former forum member if so....
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Old 02-02-2019, 10:42 AM
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Hey Mikstr, remember you from Speedzilla days....good to see you are around. No, it was stock red when i got it. Stock suspension so far as I can tell as well.
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Old 02-02-2019, 10:48 AM
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Hi

Good luck with the bike and welcome to the site

P.S. shame about Speedzilla, it was decent site... I think Larry (BLS) and Jami combined to give it a one-two, however.
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Old 02-02-2019, 10:57 AM
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Classic SpeedZilla!!! Anyways, gonna hook the TPS back up and see how it runs before adjusting. In all my searches I can not find anything about not using it...Nothing done shoddy on this bike so I would think it was removed and tied up for a reason. Guess I will find out. Can not wait to get a ride on it when it stops raining...really classic Honda.
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Old 02-02-2019, 01:24 PM
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There is no reason that I have ever heard of for running with the TPS unplugged.
Also if it is an HRC kit, first the single lift hole slide was only to be run with the short stack. You also shim the needle in the 2 hole slide .5mm higher than the needle in the single hole slide.
The needles will also look much different than all other stock or aftermarket VTR needles as they have a very long lead in or the thin part of the needle that keeps it from popping out of the needle jet at WOT.
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Old 02-02-2019, 02:39 PM
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Thanks very much for the input, especially regarding the jetting setup. The stacks are stock, airbox not hacked up, stock filter etc. I will post pictures of the needles when I tear it apart again.

I plugged in the TPS and seems to run slightly smoother but still have pretty vicious pops on decel and flames out of the exhaust. I will attempt to calibrate TPS when I pull carbs and adjust jetting next time. Would the 175/178 mains be about right for near sea level and a full Mori exhaust? Wondering if the popping is a lean condition..if it had engine mods what kind of mains would be in order?
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Old 02-03-2019, 07:48 AM
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Originally Posted by rothmans View Post
I intend to dyno the bike to see what kind of power it makes and I think that would determine if it has cams or pistons etc...no porting work on heads that I can see.

So main question is after all that...ANY reason at all TPS would be or should stay unplugged? Was there any race/track setup back in the day that did away with it?

Id be taking a look at timing (as its going on the dyno, that should be easy enough, or pull the cover and inspect the ignition advance rotor) I suppose if a specific timing curve was set up, be it it non stock ECU, non stock ignition advance rotor or both I could squint my eyes and see why the tuner might not want the TPS and ECU further adjusting the timing.
A quick internet and forum search did not get me hits on unplugging the TPS as a "MOD"....perhaps my googlefoo is weak this morning

Last edited by E.Marquez; 02-03-2019 at 10:25 AM.
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Old 02-03-2019, 07:53 AM
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I'd really wanna see the dyno plots before I started messing with any set-up. She might be a total beast up top.
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Old 02-03-2019, 09:26 AM
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Many thanks again guys...I think I will finish my normal service on it today, get it back together and see about putting it on a dyno before I try to modify any of the jetting or adjust TPS.

Unrelated question, since I got this bike somewhat in bits, had bodywork painted up, but the inner fairing air ducts (black ones) are missing inside the upper cowl...cheap on eBay so may grab but are these really critical in any way to aid cooling etc?
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Old 02-03-2019, 04:31 PM
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Originally Posted by rothmans View Post
Many thanks again guys...I think I will finish my normal service on it today, get it back together and see about putting it on a dyno before I try to modify any of the jetting or adjust TPS.

Unrelated question, since I got this bike somewhat in bits, had bodywork painted up, but the inner fairing air ducts (black ones) are missing inside the upper cowl...cheap on eBay so may grab but are these really critical in any way to aid cooling etc?
No, been running my bike without them for many years... leave them off I say
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Old 02-03-2019, 07:41 PM
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They appear to be used to deflect engine/radiator heat from the rider area. I had mine off for a bit during a warm SoCal ride, put them back on and it seemed to make quite a difference. Didn't notice any change in engine temp either way. I use them to hade my HID ballast and ignitor.
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Old 02-04-2019, 07:35 AM
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Originally Posted by mikstr View Post
No, been running my bike without them for many years... leave them off I say
I have also ran with and without them and had no issues either way

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Old 02-04-2019, 09:37 AM
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Originally Posted by CaryDG View Post
They appear to be used to deflect engine/radiator heat from the rider area. I had mine off for a bit during a warm SoCal ride, put them back on and it seemed to make quite a difference. Didn't notice any change in engine temp either way. I use them to hade my HID ballast and ignitor.
Im going to go with that ^^ with a twist, I think they intentional direct air flow to aid in cooling. Ive never ran without them on either of my SH, nor the ones Ive worked on so cant say it makes a difference
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Old 02-04-2019, 10:34 AM
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Rothmans, I’ve got a pair; it’s yours if you can cover shipping (I’m in Ontario Canada though )
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Old 02-04-2019, 11:41 AM
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Appreciate it very much...they are cheap new and plenty on eBay so I may grab some sooner or later. Gotta sort out burnt R/R plug I found yesterday and front forks first....lots of lil things to go over but this is gonna be a great bike!
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Old 02-04-2019, 12:09 PM
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Originally Posted by rothmans View Post
Gotta sort out burnt R/R plug I found yesterday
I know a guy
https://www.superhawkforum.com/forum...45-00-a-34792/
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Old 02-04-2019, 12:51 PM
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Was just reading up on that... check your PM!
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Old 02-05-2019, 09:55 AM
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any pictures of the carbs just to be nosey ..
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Old 02-05-2019, 05:29 PM
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Will post some up next time I get into them...gonna be delayed several weeks while working on other projects and travel.
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