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Discussion Starter #1
It appears that pretty much everyone upgrades their CB350 race bike to a 35mm fork. I understand that WERA and AHRMA rules allow one to fit 35mm forks and that the increased diameter should make the forks slightly stiffer and that increased fluid capacity means the oil will run slightly cooler or perhaps be less likely to overheat. But is this upgrade done for a quantifiable performance advantage on the race track or for added confidence/feel or how often is it done simply because it is convention and everyone else is doing it?

It seems to be a pain in the ass to swap front ends. Why don't more people just have their 33mm forks built up with RaceTech Gold Valve Cartridge Emulators, proper springs for the rider's weight, fresh seals and oil, and maybe a fork brace? Is it really worth the hassle to upgrade to 35mm compared to a well prepared 33mm setup?
 

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Also, if I'm not mistaken, the smallest cartridge emulator you can get is 35mm.
Most fork braces are crap and hold the forks misaligned.

But yeah, what Rosko said. And I would add that at the point at which you install, need, and use, a larger front brake. Then it's time to upgrade your forks to match.

And it's not a very difficult swap at all, depends on how you define difficult I guess. A CB550/4 front end will swap right on with minor work on the stem I think, some axle spacers, a brake stay rod etc.
JohnnyB
 

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Discussion Starter #4
I suppose nothing on a motorcycle is too difficult but the effort and amount of parts and dicking around does quickly snowball when going from 33mm to 35mm. Cartridge emulators are <$200 and can be fitted to the stock CB350 forks no problem. Springs are springs, they'll need to be upgraded for my fat ass regardless. I hear a lot of debate over the merits of fork braces. CB550 front ends don't grow on trees where I live so if anyone has a pair let me know if that is indeed the most proven route. I'd still like to hear some discussion about the merits of cartridge 33mm forks vs. damper rod 35mm forks.
 

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In some clubs cartridge emulators are "illegal", but it's hard to enforce since they can't be seen.

I ran CB550/4 forks on my CB175 based racer, up from the stock 30 or 31mm. It depends a lot on the level you are riding at. I had a worked T500 front brake and could carry the rear wheel into some turns. With that kind of loading on the front you want something pretty stiff. Would also depend on bike and rider weight. A 160 lb MT125 doesn't need very big forks, a 360 lb CB350 needs more.

While stock size forks are certainly usable, I think a lot of people upgrade to simply remove a potential area of trouble, whether it's really needed or not. I mean it is a race bike, using the best equipment affordable and reasonable only make sense. Not so much the minimum you can get away with.

As you look at bikes that run lower lap times you'll see an increase in the expense of the bike and the modifications made. So do they go faster because of the mods, or do they have the mods because they go faster. It would take an indepth study to find out. Forks swaps are considered standard procedure for many vintage racers, not so much for others, also depends on the quality of the original equipment. I went to 35's not so much because I had evidence I needed them...but because I didn't want to find myself suddenly presented with evidence I needed them bounding over the transition in T9 at 70mph while racing for a win.

In the big picture, from my experience you'd see more immediate improvements in handling by installing a set of nice rear shocks. And additionally extending the swingarm a couple of inches (varies with bike). Those changes made the most dramatic improvement in handling I ever experienced on my bike.
JohnnyB
 

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89 r2125s had 32.5 mm forks i believe. thats right. .5! try finding for seals for that.

johnnys right. with the stock front end, you could be forced into using the stock brake because of the spacing. and hes right on the emulators too.

the front end swap will end up being one of the easier things you end up doing to your racer. other things can be as much or more of a pain in the ass. also, wera allows up to 38mm in v1. possibly in gp also.

i ran a stock front end of a while. something else to think about, 32mm forks are more fragile than 35. well, i should say they bend easier.

get the best shocks you cant afford. the difference good shocks, built for you, will make is astounding.
 

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quote:Originally posted by joe c

get the best shocks you cant afford. the difference good shocks, built for you, will make is astounding.
I have no idea why this is the case... but it really is. The difference in stock shocks and set of really nice rear shocks makes is so noticable that even a brand new racer can feel it. It can turn a bike that feels unsafe to ride into a pleasure to race.

I'm big on extending the SA because many Hondas are weighted way too much to the rear in stock form. Also a couple inches seems to really settle the rear without slowing turn-in noticably. Also, alot of the CB350 guys replace the SA bushings with something stiffer, which I did to all my bikes.

I guess what I'm trying to say is... if you want to make improvements, make them in the back first. Rebuild the stock forks, throw in some 20wt and some spring spacers and spend the money on the rear end.
JohnnyB
 

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Here is a cheap set of 35mm forks.
http://cgi.ebay.com/ebaymotors/1973-HONDA-XL350-XL-350-FRONT-FORKS_W0QQitemZ280341062586QQcmdZViewItemQQptZMotorcycles_Parts_Accessories?hash=item4145a123ba&_trksid=p4506.c0.m245
This is what I have my race bike. The bottom axle clamps are 4 bolt and help rigidity. The steering stem is not a straight bolt up, but you can swap stems. I just bored the stock triples to 35mm with and adjustable straight hand reamer, from MSC, and slid the XL tubes in. That way the spacing was the same. I used the stock front brake. I have the stock XL springs in mine and they work fine for me but I weigh 240. The Xl forks are longer than stock, but I went with an extended swing arm and longer shocks to gain ground clearance. I guess I could sell you the whole set up off my bike, since I am thinking about changing over to a disk brake front end soon.

Ken
 

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Here is a cheap set of 35mm forks.
http://cgi.ebay.com/ebaymotors/1973-HONDA-XL350-XL-350-FRONT-FORKS_W0QQitemZ280341062586QQcmdZViewItemQQptZMotorcycles_Parts_Accessories?hash=item4145a123ba&_trksid=p4506.c0.m245
This is what I have my race bike. The bottom axle clamps are 4 bolt and help rigidity. The steering stem is not a straight bolt up, but you can swap stems. I just bored the stock triples to 35mm with and adjustable straight hand reamer, from MSC, and slid the XL tubes in. That way the spacing was the same. I used the stock front brake. I have the stock XL springs in mine and they work fine for me but I weigh 240. The Xl forks are longer than stock, but I went with an extended swing arm and longer shocks to gain ground clearance. I guess I could sell you the whole set up off my bike, since I am thinking about changing over to a disk brake front end soon.

Ken
 

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quote:Originally posted by freedomgli

I suppose nothing on a motorcycle is too difficult but the effort and amount of parts and dicking around does quickly snowball when going from 33mm to 35mm. Cartridge emulators are <$200 and can be fitted to the stock CB350 forks no problem. Springs are springs, they'll need to be upgraded for my fat ass regardless. I hear a lot of debate over the merits of fork braces. CB550 front ends don't grow on trees where I live so if anyone has a pair let me know if that is indeed the most proven route. I'd still like to hear some discussion about the merits of cartridge 33mm forks vs. damper rod 35mm forks.
I paid $75 for CB550 forks/triples on ebay. Like others, I picked 'em because RaceTech had the emulators/springs for that fork, and put on Works non-adjustable rears. I paid $200 for the bike...if another $1,000 for suspension/tires/brakes is too much, then you'd better pick another sport. ;)
 

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quote:Originally posted by freedomgli

I suppose nothing on a motorcycle is too difficult but the effort and amount of parts and dicking around does quickly snowball when going from 33mm to 35mm. Cartridge emulators are <$200 and can be fitted to the stock CB350 forks no problem. Springs are springs, they'll need to be upgraded for my fat ass regardless. I hear a lot of debate over the merits of fork braces. CB550 front ends don't grow on trees where I live so if anyone has a pair let me know if that is indeed the most proven route. I'd still like to hear some discussion about the merits of cartridge 33mm forks vs. damper rod 35mm forks.
I paid $75 for CB550 forks/triples on ebay. Like others, I picked 'em because RaceTech had the emulators/springs for that fork, and put on Works non-adjustable rears. I paid $200 for the bike...if another $1,000 for suspension/tires/brakes is too much, then you'd better pick another sport. ;)
 

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yeah,

one morning i went over to my local junkyard and picked up a set of 35mm cb550 fork legs (lucky me they had progressive wound springs) and a cb750 tree,both for $50. later that same morning, i stopped by the local tractor supply company and bought an assortment of their large washers for $2. then i mosied home to see what would happen. well after putting two washers in the head before inserting the lower race i had a race ready front end not long after noon, and for about $52....not including the bearings that i was able to reuse from the stock setup.

dude, there's nothing to it. no need to press different stems into different trees...but even that's not a big deal? i struggled mightily in my first year with the 33mm forks and stock brake. the front end chatter and sponginess was terrible, and the brake could fade by T3 on the first lap. i imagine you could make the 33mm much better than they are, but if you're going to install emulators and such, why not start with the best spec the class allows? oh, and to answer your question, i noticed a huge difference in my front end with the 35mm forks....and as far as i'm concerned, "added confidence/feel" is a "quantifiable performance advantage on the race track".

good luck-
tt
 

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yeah,

one morning i went over to my local junkyard and picked up a set of 35mm cb550 fork legs (lucky me they had progressive wound springs) and a cb750 tree,both for $50. later that same morning, i stopped by the local tractor supply company and bought an assortment of their large washers for $2. then i mosied home to see what would happen. well after putting two washers in the head before inserting the lower race i had a race ready front end not long after noon, and for about $52....not including the bearings that i was able to reuse from the stock setup.

dude, there's nothing to it. no need to press different stems into different trees...but even that's not a big deal? i struggled mightily in my first year with the 33mm forks and stock brake. the front end chatter and sponginess was terrible, and the brake could fade by T3 on the first lap. i imagine you could make the 33mm much better than they are, but if you're going to install emulators and such, why not start with the best spec the class allows? oh, and to answer your question, i noticed a huge difference in my front end with the 35mm forks....and as far as i'm concerned, "added confidence/feel" is a "quantifiable performance advantage on the race track".

good luck-
tt
 

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i paid $250 for an entire suzuki gt 750 front end with drum brake ( 4 leading shoe)

then i decided to buy a set of cb 550 trees from ebay for under $20... press on some tapered roller bearings onto the stem, install races in my steering tube.. and bolt together... no maching, no custom spacers... bolt together.

the 750 front end is way overkill... 35mm but it is sprung to the 750... but it does well... no chatter, great handling, and amazing stopping power with oem shoes.

tt does have a bitchen setup!!!!
 

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i paid $250 for an entire suzuki gt 750 front end with drum brake ( 4 leading shoe)

then i decided to buy a set of cb 550 trees from ebay for under $20... press on some tapered roller bearings onto the stem, install races in my steering tube.. and bolt together... no maching, no custom spacers... bolt together.

the 750 front end is way overkill... 35mm but it is sprung to the 750... but it does well... no chatter, great handling, and amazing stopping power with oem shoes.

tt does have a bitchen setup!!!!
 

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""added confidence/feel" is a "quantifiable performance advantage on the race track". "

Truer words were never spoke... .and TT is NO slouch on a race track, he's qualified to make that statement.
JohnnyB
 

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""added confidence/feel" is a "quantifiable performance advantage on the race track". "

Truer words were never spoke... .and TT is NO slouch on a race track, he's qualified to make that statement.
JohnnyB
 

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You can find 550 or 750 front ends cheap. Got one 750 front end free for one 350, and a rolling frame with front end for 50 bucks for the other 350.
 
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