Jump to content
Tyy

What can you tell me about my VF500?

Recommended Posts

To only do 110km/h means something is massively out of whack. You are messing with things that might have  small impact on performance. You have a gaping chasm in performance. Is it actually running on all 4 cylinders? Is a brake binding? You have lost over half the horsepower of the engine so something very drastic is amiss. You need to go right back to basics and check all the fundamental things, like plugs, firing all on four, blocked air filter, fuel to all four carbs. 

Share this post


Link to post
Share on other sites

The (TCI) ignigition timing cannot be adjusted (according to the book).

 

and just to be sure, you are talking 110KM/H right? (u are in Canada) 

Share this post


Link to post
Share on other sites

Kilometers per hour. I have checked and rechecked all the major things. I have a suspicion that I was hoping one of you might reiterate to save me the embarrassment. I think it is still just running overwhelmingly rich. I am going to open up the air box and see if it makes a difference, and hopefully confirm something.

Share this post


Link to post
Share on other sites

Does it need the choke when cold? If it was massively rich it would start without the choke. It would have to be hugely rich to limit to 110km/h. It would stink of petrol and be blowing black smoke. 

Share this post


Link to post
Share on other sites

I just got back from a ride without the air filter. I did not find the dead spot at the top of my rpms. I took it on the highway and it was still pulling me forward at 120kmph. I let off though because it was screaming like a banshee. Overall I think the leaner mixture is way better for it. How many jet sizes back from 117.5 should I go to simulate no air filter? It does take a little choke or twist of the throttle to get it started in one shot.

Share this post


Link to post
Share on other sites

I've got some science and a video to share. I had a thought last night and looked up the rear wheel size on the magna. Turns out the tire sidewall makes up for the difference in the circumference of the 16' wheel, but while I was at it I used the same gearing calculator to determine what rpm I am riding at to get a top speed of 120. The rpm needed to reach 120kmph with my gear/wheel/tire setup is 6200rpm, for reference the max possible speed is 218kmph at 12000rpm. This calculator does not include any power numbers. I would assume because the power doesnt relate to the top speed, only how long it takes to get there. With this said, I could potentially reach a higher speed if I gave the engine more time to do it or if I milk more power out. Although I am not too keen about holding it up that high for very long. I want to insert a clip onboard a magna to show you what it sounds like on my end.
https://youtu.be/tOpbJvGbbrY?t=88

(Pardon the hysterical squealing in this video hahah)

 

This is a video I took yesterday to show you how it sounds now without the air filter

 

I want to note that I am fairly happy with the bikes performance now. I want to hear any suggestions though about jet sizes or maybe your opinion on running no air filter. I owe you guys a thank you too, @jeremyr62 @Dutchy @TheDutchy @Forbes

 

 

Share this post


Link to post
Share on other sites

Would think power has a lot to do....120km/h is around the breakthrough wind resistance where you use more fuel than if you were cruising at 110.
It's been a good few years, but 750 top speed listed around the 205km/h Mark, had mine around there on clock, but imagine in reality it was around 190 odd...

Sent from my HTC_PN071 using Tapatalk

Share this post


Link to post
Share on other sites

From that video you are short shifting. Don't be afraid of revving the engine. It's what it is designed for. Some claim you shouldn't go above 9K rpm to save the valves but I don't subscribe to that theory. 

Share this post


Link to post
Share on other sites

and as for running w/o an air filter......

 

Here what I shook from the K&N's in my RC51/SP (shortly after I bought it)

 

IMG_0054 (2).jpg

 

 

Granted, the inlet tract on a SP is "straight" (to the point that Honda let it run through the headstock), but you really donot want any of the above sucked into your carbs....

 

 

Share this post


Link to post
Share on other sites
8 hours ago, jeremyr62 said:

From that video you are short shifting. Don't be afraid of revving the engine. It's what it is designed for. Some claim you shouldn't go above 9K rpm to save the valves but I don't subscribe to that theory. 

 

I can tell there is a lot more to stretch out, but I definitely have thoughts of high rpm valve carnage in the back of my head.

 

7 hours ago, Dutchy said:

but you really donot want any of the above sucked into your carbs....

 

 

 

What setup were you running with 112's exactly? I honestly dont know how many sizes down I should go because without the filter on, this thing seems to be in its sweet spot now

Share this post


Link to post
Share on other sites

I have not messed with the carbs, maybe the prior owner did....

 

 

 

Share this post


Link to post
Share on other sites

As above, drop the jet sizes...

 

We are running 112 with open box, open baffles... For street use, I would not recommend that.. But it is an indication that at least you have to resize the 117's below the 112's.. (98/95 is a maybe, you have to trial and error these jetsizes)

 

Listening to your vid., you take her to about 5krpm. That is about where the main jets start to take over. If you take her above 6k and she starts to stumble heavy at 6 , 7, 8, 9 krpm. The jets are to big.. The engine is choking on the amount of fuel...

 

And yes, the engine won't mind, neither get hurt taking her beyond 9krpm..  Here the VF500F with a modified '86 engine running on track.. Look at the rpm's

 

 

The earlier '84 and '85 engines have issues if you run her above 9k for extensive periods.. It will run the conrod bearings out.. The 1986 versions have a modified oilsump and pump that takes care of it.. This same VF500F also runs 4 hour Endurance events.. Imagine a VF500F run for four hours on that same track as in the vid... I know she held up fine..

 

It took me 8 times getting the carbs out / swapping jets / building the carbs back in / balancing them / and test ride it.. Once we got it right, we never needed to go back into the carbs again.. 

Share this post


Link to post
Share on other sites
4 hours ago, TheDutchy said:

As above, drop the jet sizes...

 

We are running 112 with open box, open baffles... For street use, I would not recommend that.. But it is an indication that at least you have to resize the 117's below the 112's.. (98/95 is a maybe, you have to trial and error these jetsizes)

 

 

 

I am curious whether you run offset front and rear cylinder jet sizes? Would this difference be due to unequal length headers? The pipe I have on now has a lot of unnecessary bends that make me think it is an equal length setup. Also I wanted to mention that I have upped the slow jet by 2 sizes, I want to say its a 48 now. This fuel ratio issue totally describes the trouble I have been having once I get into 6krpms and up. Also that is a sweet video

Share this post


Link to post
Share on other sites

The slow jet is standard #38.. I wouldn't go beyond #40 on the slow jet. On most of the VF series the slow jet is #38. On my VF750 street bike the slowjet is #40. On the VF750 endurance racer, the slow jet is #42.  I would recommend to install #40 on the slow jet.

 

On the main jet, it is a different story, it is depending on what carb code is installed. The carb code is printed on the side of each carb housing, just above the mating surface of the float bowl. Different carbcode means different main jet sizes. Standard they came with:

1984 #108 mains all around..

1985 VD41A A  #90 #92

1985 VD41A B #92 #95

1986 #92 #95

 

The differences are caused by: Different breather lines on the float bowls, different emulsion tubes on the main jets, different vac. slide/membrane, fuel pump / gravity fed..

 

So, determine the carb code, lower the size of the slow jet, lower the size on the main jet..

 

 

Share this post


Link to post
Share on other sites

I did read somewhere about one carb being jetted differently from the other three, I think on one of the VFR's to correct scavenging issues with the exhaust. Our VF'S run downdraft carbs on the front and sidedraft carbs to the rear....the characteristics of each, flow, gravity etc would be different so a possibility why different jetting!

Sent from my HTC_PN071 using Tapatalk

Share this post


Link to post
Share on other sites
5 hours ago, TheDutchy said:

The slow jet is standard #38.. I wouldn't go beyond #40 on the slow jet. On most of the VF series the slow jet is #38. On my VF750 street bike the slowjet is #40. On the VF750 endurance racer, the slow jet is #42.  I would recommend to install #40 on the slow jet.

 

On the main jet, it is a different story, it is depending on what carb code is installed. The carb code is printed on the side of each carb housing, just above the mating surface of the float bowl. Different carbcode means different main jet sizes. Standard they came with:

1984 #108 mains all around..

1985 VD41A A  #90 #92

1985 VD41A B #92 #95

1986 #92 #95

 

The differences are caused by: Different breather lines on the float bowls, different emulsion tubes on the main jets, different vac. slide/membrane, fuel pump / gravity fed..

 

So, determine the carb code, lower the size of the slow jet, lower the size on the main jet..

 

 

 

Please follow this advice.  He is absolutely right.  I have gotten away with some 42 pilots on some of my bikes depending on mods, but 40 is the sweet spot for the 500.  

Share this post


Link to post
Share on other sites
22 hours ago, TheDutchy said:

 

 

 

 

This is a "track"?!!!!   I can't believe they allow people to stand right at the end of the straights.

 

Don't get me wrong, I would run it in an instant, but HOLY SHIT!  Seems really un safe.

Share this post


Link to post
Share on other sites
26 minutes ago, Captain 80s said:

 

This is a "track"?!!!!   I can't believe they allow people to stand right at the end of the straights.

 

Don't get me wrong, I would run it in an instant, but HOLY SHIT!  Seems really un safe.

 

Yup, this is a track.... It's an abandoned military base in Germany...

 

In classic events, we don't call it racing, it's a "Test Skill Ride"..  And yes I do agree it has a certain risk level...

On this german event, the levels are elevated, other events, even have higher risk elements, like racing over cobble stones through city streets...

 

Wasn't it The Boss singing about racing in the Streets ?

 

 

Share this post


Link to post
Share on other sites

Or they call 'm "consistency runs", a track made on a industrial estate....   

the winner in theory is he who reaches the most consistent laptimes, but they still give it some welly...

 

 

 

Share this post


Link to post
Share on other sites
23 minutes ago, Dutchy said:

Or they call 'm "consistency runs", a track made on a industrial estate....   

the winner in theory is he who reaches the most consistent laptimes, but they still give it some welly...

 

 

 

 

Whatever they call 'em...   I wish they did that around here.  But there is NO WAY IN HELL that could happen here in the States, no matter how many waivers were signed.

Share this post


Link to post
Share on other sites

Go little "Mini-Ceptor"...

 

Before Mr.RC45 I had a love affair with my 86 VF500F Interceptor
bought new from Golden Gate Cycles... I modified it extensively...
Dymags... Billet Clutch basket... Exhaust and even converted the chain
to belt... This became famous Belt-0-Ceptor... I racked up 98,000
trouble free miles... I sold it to my Air Force buddy up in White City
Oregon...
ce5BVi3.jpg
gallery_3131_51_14630.jpg

 

Home made Billet Clutch Basket
gallery_3131_51_1687.jpg

 

My custom dash with Oh Shit warning...
gallery_3131_51_36605.jpg


Sometimes being the "Mini-Ceptor" among the Big-Bad-Motors of Death can be a recipe for bruised egos...
qBUdODI.jpg

Share this post


Link to post
Share on other sites
On 12/7/2017 at 3:16 PM, BusyLittleShop said:

gallery_3131_51_14630.jpg

 

 

 

What have you got that seat covered in? I am also curious what your wheel setup is in this picture because those look like radial tires!

 

On 12/7/2017 at 5:11 AM, TheDutchy said:

Different carbcode means different main jet sizes. Standard they came with:

1984 #108 mains all around..

1985 VD41A A  #90 #92

1985 VD41A B #92 #95

1986 #92 #95

 

I just found something weird out. The jets I took out of my carbs were sizes 102 and 105. The frame is a 1984 bike, so I would have thought they were the same size and larger given it was jetted for a custom exhaust. The only markings I can find are VD on the side and a code that reads: 5 6 B (triangle) W D (and a Japanese letter). The slow jets I took out were 38s, so I definitely have 40s installed. I am going to go with 108s for the main jets. I'm assuming someone more qualified than me set up the carbs and Henkel pipe at the same time, so 3 sizes bigger should account for uncorking the supertrapp and a K&N right?

Share this post


Link to post
Share on other sites
3 hours ago, Tyy said:

I am also curious what your wheel setup is in this picture because those look like radial tires!

 

It looks like that might be a real Dymag wheel.  It's configuration without a cush drive would help adapting the custom belt pulley.  It would be wider than stock and could take a wider, lower profile tire.  Perhaps even a radial.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


×