Yoshimura Reissue for the VF500F

I heard back from Yoshimura this afternoon.

They are considering re-issuing their 4-2 system for the VF500F! I don't know if I can chalk this up to my letter writing skills but I did say their system was the cat's pajamas back in the day so maybe this email got to the right desk ;-)

This said, they would like to get an idea of how many owners would would be interested in a group buy.

I'm a fan of the way the Yoshi system looks and I've read that the 4-2 systems work really well on the VF500F. The only caveat I see is that you will need to remove the stock centerstand to install.

If there is interest please send me an email and I will add your name to the list of people interested in purchasing.

Also, if anyone out there has very detailed photos of this system (on/or off the bike) Yoshi's R&D department has requested this for their reference, as a first step. Thx!

 

Wow.....way to go.

Can someone write a letter to a company that'll make a valve-train for the VF500 that doesn't blow?


Seriously though ic, good work.

 

If it costs a thousand bucks forget it, but if they can make one for 400 bucks or so I'm in. Honestly I'd be happy to have someone make slip-ons that fit...

 

I'm interested depending on the cost. Did they give you a ballpark price? Any idea on the volume they're looking for in order for them to justify their time / effort? This is a great first step - at least they're thinking about it. Thanks for sharing with us.

 

Thank you for the post.

As a first step they have asked for a tally of owners who may be interested. I agree the price point is important - hopefully we will have enough owners (I am a member here and the Yahoo VF500F Group and have posted on both forums) to rouse Yoshimura's interest.

I'll update the thread as I receive feedback. In the interim please feel free to get the word out to other owners in local groups or other web forums. Thx!

 

Slip-ons are one way to go but these tend to rob power . Even with proper re-jetting you are likely to only get back to the stock HP rating.

4-2 systems, like the Yoshimura - from what I have read - are a very good match for the VF500F.

Thx!

 

I've been looking into this - hardfaced cams, rockers and valve spring kits for the VF500F - but this is for another post...

 

Valves and springs ASAP!!!! Oh, and reasonable pricing as well!

I'd be very interested in a nice 4-2 system. Ofg course, without a price estimate, there's no way of a commitment, but definate interest here, as long as I get the valves and springs!

 

Thank you for the post. I'll add your name as an interested owner. I really don't know where the price point will come in - if Yoshimura does decide to reissue their 4-2 system.

At the very least it is very cool that they are entertaining the idea.

I am a little ways off on posting my findings on the valve springs but there is a company that makes a kit for the VTR250 (which shares the same valve springs as the VF500F). They said that they would take a look at making a set for the VF500F if I sent them a used head for reference – have to finish my 17” wheel conversion first, before I tackle this.

 

I've tried to keep my finger on the pulse of this topic for the past 7-8 years. I've got a 4-1 system designed but never moved forward beyond the prototype stage. The reason is simple - the demand is just not there. I'd say it's about 10-15 up front with maybe 5-10 per year after that. And don't foget that's at a $400-600 price point. It's not likely someone will buy a $1200 exhaust for an $800 bike.

A couple of other comments:
- I'd ask what minmum they would need. If it's 30-40-50-more then forget it, you'll never get that much. If they will do 10 systems then you might have something.
- The Yosh 4-2's were not that great. Of course, they will say their stuff is the best, do you expect anything else? A 4-1 has always been the best performing system but also much more difficult to design.
- It concerns me that they want pictures of someone's bike with their product on it. It seems like they should already have that design somewhere.

Let us know what you find out!

 

Thank you for the insight Jamie.

I had read that 4-2's were better than 4-1's but it doesn't appear that this is correct.

In terms of engine performance - is the stock system best followed by a 4-1 system, a 4-2 system and then slip-ons?

It seems like all the aftermarket systems tend to cause jetting and loss of horsepower issues..?

Are there other manufacturers beside Hindle that made a 4-1 system for the VF500F?

I agree that the owner interest – I posted an inquiry on the Yahoo VF500F Group and VFRD as well – isn’t there. I have only had a handful of responses.

Based on this I think this idea is a non-flyer. I do want to tip my hat to Yoshimura for, at the very least, answering my email and considering the idea – I think this reflects positively on their company.

This said, I would be interested though to learn more about the DMr 4-1 system. How far have you gotten with the design. Is this based on the Hindle (or other manufacturer’s) system?

Thx!

 

Yosh also made a 4-1, but I've only ever heard of one single system making it into the US. They were sweet, too bad the guys at Yosh R&D can't find the info on that one. Kerker/V&H also made a 4-2. Here are some thoughts on exhaust design for the V4's:

Phasing - The whole problem is that each bank is separated by a 90° phase shift. With the 'big bang' design in MotoGP many people now understand this concept of uneven firing order. That whole concept is to space out the power pulses unevenly. What this also produces is exhaust pulses that also come out unevenly. If you made a header with four equal length primary tubes you would have the pulses that are close together hitting the collector about the same time, which chokes them out. After that you have a dead time where no gasses come out and you lose any scavenging effects. The solution is to tweak the length of the primary tubes to balance this out. Another problem pops up - the flow losses vary by engine rpm. That means you have to design a V4 system for a particular rpm range, thus the big dip in power in the midrange. The stock Honda systems are designed to minimize this dip and in the process it also reduces top end performance.

Power and Weight - Overall you should not expect huge gains. Maybe 2-3hp on top for a 4-1, and maybe 1-2hp for a 4-2. Top end losses are not uncommon with slip-ons. At best a set of slip-ons will net you stock output. The weight of the stock exhaust system is not as much as some think, so weight loss isn't really significant. Expect maybe 20lb or so.

Jetting - Normally a 4-1 or 4-2 will not require different main jets. The stock jetting on the top end is not especially lean. The problems are in the midrange, which is where the slide needle controls the mixture. Unless you have other internal engine mods (like high compression pistons or cams) a simple shim under the stock slide needle cleans things up and a full jet kit is not required.


The header that I've designed is loosely based on the Hindle system. There are some things I don't really like about it so I want to see what improvements I can make. I'm not concerned about the center stand as I ditch those as soon as I buy a bike anyway. A swingarm stand is just as useful and I don't have to carry it everywhere I go. I've also noticed a theoretical imbalance in the flow in the Hindle system. Only dyno testing will show if that equates to the real world. Right now the big hurdle is cost. To make just the primary tubes I've gotten quotes anywhere from $1000-1500. That's not even including a collector, welding or a muffler. That's why I designed my own mandrel bender that would be dedicated to just this task. I've got some of the parts and off-and-on will be making the rest. This has been going on for several years now so don't expect something anytime soon. The VF1000 systems would be first, then the 500 and the 700/750 models last. If you see that I've made a system for the 1000's you'll know that I'm close, until then it's just a "one day" kind of thing.

 

Many thanks for the clearly written post!

This is very helpful and I really appreciate your taking the time to write out these thoughts on the various exhaust systems for the VF500F.

With the new intel - I'll write to Yoshimura and see if they can dust off their 'VF500F 4-1' file (I didn't originally inquire about this as I didn't know that they had produced one).

As you have noted - based on the lack of current owner interest Yoshimura probably won't consider making a limited run...but it's worth a try.

 

That Jamie guy is one smart fella!

I do have to say that I'm interested in a full exhaust system more for the sound than looks, or HP gains. As long as there wouldn't be a huge loss, I would be ok with dropping a HP. Actually, I could see where dropping the power range down in the RPM band would be a good thing, as well.

 

I still think it would be nice to know what the minimum quantity would need to be. It would be a shame to get 8 people interested and have the thing fizzle out when Yosh only needs 10. If the possibility was good, I think more folks would step up to the plate.

 

I agree, I sent an email to my contact at Yoshimura and am waiting to hear back. I did inquire about the 4-1 system as well - maybe they have a dust covered file, in the basement somewhere, with the spec's. I'll keep everyone posted.

 

If I had some extra $ around, and 2 more would be all it took to get them rolling on it, I'm sure they woudl sell! Look at how well they sell on Ebay!

 

Hurry up with this post ;-)

 

I'd only be interested if it was the 4-1

 

I need to track down a spare set of heads to send the the valve spring company (as noted they make a kit for the VTR250 which shares the same valve spring part numbers as the VF500F) as a first step to dialing in the correct springs. I have this on the clipboard for later this year.