CBR F4 track bike suspension upgrades

[MattR302]

So last winter I picked up a rough condition F4 as a cheap beater track bike. Spent a few bucks getting it rideable, and did 5 track days on it. This winter I'm looking to upgrade the suspension a little without spending a ton. I'm about 195lbs, and a fast-ish red group rider. For the front I plan on respringing and refreshing the forks.

For the rear, I've got an opportunity to pick up an older Penske 8981 double clicker (6 clicks of adjustment) for $220 in unknown condition, so figure another $250 for a rebuild. But a local suspension guy says that $220 is a decent price for that shock in freshly rebuilt condition, not as is. So my question is, do I spend $470 on that shock, or is there a better <$500 back-for-the-buck option?

[theducman]

Buy it and have it re done

[Petorius]

I stalked the interwebs for a newer penske double for a while a few years back. $500 seemed to be the low end, if that helps

[butcher bergs]

I would love to know what mystical place "local suspension guy" has seen those go for $220 without needing a rebuild.

[OreoGaborio]

I would love to know what mystical place "local suspension guy" has seen those go for $220 without needing a rebuild.

Just talked with this local suspension guy on the phone the other day. I guess that "mystical place" was Street & Comp.

His opinion was that a 7 year old (at BEST since it was discontinued in Aug. 2007) 8981 with only 6 clicks of comp adjustment that's worn out & needs a complete top to bottom overhaul isn't worth all that much money. Prob not gonna find another FRESH one for that cheap, but he also wasn't sure it was worth the asking price + overhaul cost.


My opinion is that it's probably not a horrible deal, but you can prob get a younger, better 8983 for about the same price.


(Prob not a good idea to be a dick about someone's opinion when you don't even know who that person is.)

[loudbeard]

Unless something is wrong with your current shock or you have a money tree, I'd leave what you have in there. Any particular reason you're looking to upgrade?

[butcher bergs]

Wasn't being a dick, Pete and I dont really care who said what.
Not once have I seen a fresh one going for anything under 400 anywhere ever (which is not an opinion), hence my curiosity as to where this mystical place was that had these prices. Not saying it's impossible, I simply have my doubts.

[jasnmar]

Respring and refresh of the front suspension, plus purchase of a worn aftermarket shock plus a rebuild of the shock is exactly what I did with my F4.
My shock happened to be a Fox Racing shock but it's probably in the same class as the penske.
Sounds like a reasonable plan at your level of riding. If you are planning on competing with the fastest of the middle weights I'd say buy once cry once, but you probably aren't on the right bike if that's your goal.

[MattR302]

Thanks guys. My question was is there was any better budget rear upgrades I should do instead, like rebuild the stock shock, or swapping an OEM shock from a newer bike, etc. Or if you thought that Penske was a good enough deal for my level of riding that I should go that route.

[OreoGaborio]

Go the Penske route.

Just not sure if the one you're looking at is the one for you. Dont have enough info.

[loudbeard]

If you bring Kates the shock (not installed in the bike) budget about $275 for parts and labor to spring it for your weight and rebuild the rest of the shock.

[butcher bergs]

Don't waste any time with the OEM shock. Pull it then sell it or throw it away.

Have the Penske refreshed and, unless "unknown condition" ends up equaling total junk, don't worry about the "value" of refreshing it because I'm guessing you're not in it for the equity.


Next thing you're going to want to do is raise the ride height front and rear on that bike. For reference, the ride height on my F4i is maxed out on both ends. For me it was the only way to prevent the machine from squirming under braking while turning in. Not sure why but the front won't push nearly as much on the exit either. Haven't looked at my set up in a while but if you want numbers let me know and I'll take some measurements.

Buy the Penske.

[jasnmar]

There is a guy out there who specializes in Rebuilding CBR shocks (mostly for installation in VFRs). You can send him your stock shock and assuming he does a respring and revalve you'll be somewhere in the neighborhood of $250 into a $40 shock.

Go after market. Whether it's Penske, Elka, Fox, or other reputable aftermarket manufacturer isn't incredibly important at your riding level (or mine), but don't throw a bunch of money at something that won't have value later.

If you want to ignore our advice I have an F4 and an F4i shock sitting around that I'll make you a deal on... ;-)

[gmdboston]

Penske Shock rebuild:

Labor $95
Rebuild Kit $67.50
Shock Spring ( if you need an alternate rate) $115

Total $277.50
Shock cost $220
Total $497.50

New 8983 $925.

As long as 'Unknown Condition" isn't burned to a crisp and run over by a train.

[MattR302]

It's in good physical condition, just unknown when the last rebuild or service was. The bump stop piece is kinda dry rot cracked though.

[gmdboston]

It's in good physical condition, just unknown when the last rebuild or service was. The bump stop piece is kinda dry rot cracked though.

Looks good enough, Bump Rubber will add $20. For the 99 F4 a #950 spring is what we used for a 170-220 lb rider. The spring rate is engraved on the end of the spring.

[MattR302]

So I ended up picking up that Penske shown above, it came with two springs. The one off the shock I think is a 550, the other one is much beefier.


Trying to figure out my plan for the front forks, I think I'm just going to do a re-spring and new oil, probably not doing the valves at this time. But I'm thinking that since the bike has 33k miles on it, I might want to do new seals and bushings too while I'm at it. Is re-springing the forks just a straight swap, or are there new shim lengths that need to be calculated too? I've done fork seals on my old 2000 ZX6R myself, trying to figure out if I want to tackle this job on my own or have it done when I have the shock rebuilt.

[jasnmar]

You'll need to re-shim to set the pre-load correctly. Mine took me a couple tries to get the shims cut correctly.

Plan on replacing seals and bushings as long as you're taking stuff apart.

[MattR302]

You'll need to re-shim to set the pre-load correctly. Mine took me a couple tries to get the shims cut correctly.

I'm guessing that means assembling the forks, mounting them and the wheel back on the bike, measuring the sag, cursing, disassembling everything, cut new shims, reassembling everything, mounting everything again, etc...

[jasnmar]

Lol. That's (almost) the way I did it, but I'm a bit of an idiot.

The direction I got from Racetech were a bit generic, and I misunderstood the different types of caps in the instructions. This caused me to cut the spacers too long the first time and when I put them on the bike the sag was almost 0... Went back to the instructions, realized my problem and cut new spacers.

I took the wheel and forks back off to fix it, but that technically wasn't necessary. I could have just replaced the spacers "in place", but I lacked confidence to do so.

The directions really weren't all that hard to understand, I just screwed up. It's pretty straight forward.