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extreme heat causing rear shock problems?


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Hello, I have been having this reoccurring nightmare.. every time i take my bike out (1992 vfr750) she seems to handle just fine.  But starts getting sketchy the longer I ride.  it feels like the rear end is all over the place.  so i thought it might be tire pressure, no.  front forks tweeked, i dont think so. wheels aligned and plumb, yes.  So yesterday after limping her home i started to do some poking around with one of those laser thermometers and 10 minutes  after i shut down my bike the rear shock was still at almost 200 degrees F!  it was hotter than the exhaust pipe tat happens to be like 2 inches away.  also i was pushing up and down on the rear end and it seemed really soft.  i have a nice Penske emulsion shock, i believe it is called.  no reservior, but i think it is at least 2 way adjustable.  the shock is something the previous owner must have bought and i did notice that my bike came with this almost $1000 shock the day i bought it.  thats why i might not have suspected the shock was the issues weeks ago.  I guess I'm just wondering if anyone else has had this issue and any possible reasonably price cures.  I have to head back outside to put my bike back together.  I tore it all apart yesterday to try to get a better look at that shock, which wasnt a very good idea since i have no game plan as to where to go from here.  Im just going to put it back together before I start loosing nuts, bolt, etc...

Thanks in advance for any opinions on this matter

jesse

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I’m not familiar with that shock but it sounds like it needs a professional overhaul and regas 

 

Do you know how old it is?

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Regularly ridden, street suspensions need serviced bi-annually. Track suspensions need done annually. 
 

Over time/use, oil loses its viscosity and thins out. Heat only exacerbates this. I’d say, your shock definitely needs serviced, at the minimum. It may need to be resprung and valved to your weight and usage, as well. I’ve used Traxxion Dynamics for all my suspension work, for nearly 15yrs, covering four bikes, and highly recommend them. I’d talk to them about doing your forks, as well. I have their setup, springs, and Axxion valves in my VFR forks (SV too), though, I’ve had their cartridges in two other bikes, as well. A fresh, properly set up suspension, F&R, will transform the bike. It’s definitely worth the investment. 

Dan Anderson @

https://traxxion.com

 

The only emulsion shock Penske offer is their 8900. It’s rebound- and length-adjustable. I have one on my SV and are a really nice street shock.
 

The VFR is bad for cooking shocks. When I discussed a fitment for my 5th Gen, that was a concern of Dan at Traxxion and Eric at Penske, because of my intent to track the bike. Ultimately, I went with a custom-length 8983. It’s built to be the longest I can fit, to raise rear ride height to the maximum. And, has a reservoir for maximum fluid capacity, to battle the VFR’s heat. 
 

Those who’ve ridden my 5th Gen, including a 6th Gen owner, have raved about the suspension and handling. I feel the same and wouldn’t change anything about it. 

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Thanks for the advice guys.  As for the question of the age of the shock, I'm not sure.  If I had to guess I'd say 10 years old at least.  The reasoning behind that is the person I bought the bike from owned it for 10 years and only put 10,000 miles on it.  It was clear to me when speaking to him that he wasn't much of  a " motorcycle type guy".  Who sells a bike and doesn't mention, Hey, by the way it also has an almost $1,000 Penske shock in the rear.  several other modifications became clear to me as soon as I got it home.  First thing was the color codes on the sub frame say its a blue color.  But my bike is all red.  I might possibly have the only red 1992 vfr 750 because I'm  pretty sure in 1992 blue was the only color option.  Please correct me if I'm wrong.  This isn't my first motorcycle but it is my first vfr.  It also has a dynojet carb kit.  Don't know much about that and not sure what stage is installed on my bike.  Actually I'm not 100% sure if it even has that mod, but my bike does have the "dynojet" sticker on it, so good enough either way,  right?  The last mod and probably my favorite is the carbon fiber two brothers slip on that is on the left side of the bike.  Not only does it sound bad ass but on the right side no swing arm, chain, sprocket, or muffler.  All that you can see on the right rear is a big ol' 8 spoke!  Love it!  But Anyway, sorry got a little off topic bragging on my bike.  The point of that was the second owner, the guy I bought it from didn't mention any of those modifications, which leads me to believe he purchased the bike in that configuration.   So back to the shock, its seems it probably needs to be taken out of the bike and operated on, weather its from 200 degree F heat or not,  doesn't really matter now, the damage is done.  But looking at the big picture something is going to have to be done to remedy the extreme heat coming off the header next to the rear shock.  its not only the shock getting cooked but also the battery ,starter relay, and R/R. The rear brake reservoir and lines are looking pretty crispy also.   And i cant leave out my leg!!  I know I'm not the only one with this problem and I'm sure that someone out there has a cure.  Unfortunately I havent been able to find anything yet.  This is how much luck i'm having...After I posted my original question at the top of this page I took a break from it all.  A couple of hours later I search for "excessive heat rear shock vfr 750" and the first search result is my original post on the top of this page!  That has never happened to me before.  I think I can say I've come around, full circle.  BUT STILL NEED ADVISE

THANKS

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All VFR’s are like this, so I don’t see it being specific to you or as much of an issue as you’re making yourself believe. It’s going to be more the issue of soft bits that are 28yrs-old. I know a guy with four 3rd Gens and has zero issues. But, he has stripped them down and gone through every last bit, replacing and servicing their every need. You’re going to have to do the same. It’s part of old bike ownership. 

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All VFR’s may have left the factory like that but not all are like that now. I made & fitted a heat shield between the rear headers & shock on mine & the left side NACA duct directs cool air at the shock. Never experienced fade in my Nitron remote reservoir  shock 🙂

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Umm...TBR didn't make an RC36 left-exit slip-on...

 

You may have a genuine TBR full system on there.  Post some pics and we'll be able to tell you for sure.

 

Someone swapped plastic or re-sprayed the OEM panels; there were no R-157 red US-spec VFRs in 1992.  What color are the wheels?  OEM color in the US was Granite blue metallic (which is often confused for black) with dark silver wheels.  Check out my brochures: https://www.vsource.org/VFR-RVF_files/Brochures_RC36.htm

 

Ciao,

 

JZH

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hey thanks for getting back at to me Im very curious about this bikes past.  ok maybe saying a "two brothers slip on" was incorrect.  It is definitely a carbon fiber two brothers racing "muffler" for lack of a better term.  But its definitely on the left side.  I will takes some pics when it gets light out.  As for the color, the label on the sub frame, about the rear inner fender the code is for the blue matallic, but my bike is red. The gas tank, with honda decals.  Fairings with VFR decals, the whole 9.  So the original owner must have actually swapped fairings, tank, etc. with a 1991?  1993? because i cannot see any signs of a repaint.  I am a painter by trade and can usually spot non factory paint jobs pretty easily.   hopefully it wasnt done to cover up a crash.  But then you probably wouldn't change it to a color that wasn't an option for that year.  Kind of a dead give a way.  As for the wheels they are both black.  they also look like they have factory quality paint.   It seems to me the original owner put some money into customizing this bike and 'Im glad he/she did if that is the case.  I will post some pics shortly and hopefully get to the bottom of this.  Oh yeah, my original problem, with the Penske rear shock getting almost 200 degrees F after a 10-20 minute ride and turning soft as baby shit, I still haven't gotten to the bottom of that yet.  So more than happy to hear suggestions.  If anyone is willing to share their knowledge and experience with Penske shocks on vfr's Im all ears on that subject as well!

Thanks again everyone who was/is willing to share their know how with someone they don't even know!  MUCH APPRECIATION 

Jesse

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I have an old Penske shock on my Y2k and, before I had it rebuilt, it would sort of sack down during the ride and about five minutes after I parked some pressure would get released and the rear of the bike would rise up about two inches.  Freaky.

 

Ed Sorbo at Lindemann in California rebuilt it for me.

 

The bike's vintage can be determined by the VIN, so if it has an "M" in the tenth position, it is a '91, an "N", it's a '92 and a "P", it's a '93.  The subframe could have been replaced at some point, but altering the VIN would be very unlikely.  Something's not right, but in theory it could have been an insurance crash job... When I decked my '90 back in California ca. 1991 it was repaired by a Honda dealer with all new body parts.  Most of them were damaged, IIRC.  It is possible that finding new red panels was easier than finding blue ones when your bike went down (sorry!)  https://www.vsource.org/VFR-RVF_files/BVINSystem.htm

 

Ciao,

 

JZH

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Something you might try is increasing the rebound damping. That will help when the oil thins out from the heat. Kind of a bandaid, but it will make it wallow less.

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