350X Front Fork Damping 3Wheeling Mag Article

[tgmartz]

There was an article in one of the 3Wheeling Magazine issues on how to modify the damping tubes in the front forks to slow down rebound damping on the 350X front forks. Does anyone still have a copy of this article or have the info? I have a 350X that I would like to modify the front forks on.

[dovesprings250R]

I'd like to do that to mine too. Mine is springy rebound and tops out a bit too. This article would be nice. I would think just adding heavier weight oil and more of it might fix it.

[Troll]

Here's a good tip; http://www.3wheeler.org/vb/showthread.php?t=10244 .................:thumbsup:

[dovesprings250R]

Informative. Thanks!

[Black Sheep]

There was an article in one of the 3Wheeling Magazine issues on how to modify the damping tubes in the front forks to slow down rebound damping on the 350X front forks. Does anyone still have a copy of this article or have the info? I have a 350X that I would like to modify the front forks on.


the modification you are refuring to was the installation of Terry Fork Kit damping Rods. I had a set in one of my 85 350X's. they have not been avalible since the late 80's. I then set out to find an alternative for ither 350X's and i discovered the 83/84 250R damping rods were almost the same as the terry fork kit. In addition to either damping rods running progressive suspension fork springs will get your forks up to par with todays recreational quads suspension.

The Link Troll posted is the write up explaining the modification

[tgmartz]

The modification that I am referring to did not include any other parts. It required that you braze closed a large hole and then re-drill a smaller hole in the same place. I have performed this modification twice but it has been over 20 yrs since the last time I did this and I can't remember which hole to braze closed and the size of the hole to re-drill.

[hrc200x]

I know exactly of the article your talking about, I think a board member by the name of waterpumper sent it to me, I'll have to do some digging around on my computer and see if I can find it.

[hrc200x]

Lucked out there, first placed I looked. Thank you waterpumper.

[dovesprings250R]

Nice! I'm gonna do this to mine asap. Hopefully before the trike rally. I'll give a full report on the changes.

[NOS_350X]

im pulling appart my 350x forks toamrow probably

[dovesprings250R]

You gonna do this to em? Seems like a great idea.

[NOS_350X]

Well my fork seals are blown, have been fore a while. I have a good way of tempoarly fixing them. I gess now i will just tear it appart. Never done forks before, ive always been afraid.

[tgmartz]

Thanks sooooo much! This will fix my problem! Appreciate all your help!

[jenndnn3]

Any possibilty those that will do this, posts some picts of the progress with some descriptions??:hail:

And Tgmartz welcome to the boards!

[NOS_350X]

Got it appart right now and came on here to find out exactly what part need the work. sorry guys no camera tonight.

[dovesprings250R]

I'll post step by step photos when I do it. I can't weld but my dad and brother can.

[NOS_350X]

Im going trail riding thursday, should have it all together by then. So brent i can tell if its worthd doing it. I suspect its going to be a night and day diffrence for me. When pulling it appart clumps of oil dirt and crap fell out, it was way overdue.

My bikes RUN but ive never touched any suspension before. Its all a first for me.

[dovesprings250R]

Im going trail riding thursday, should have it all together by then. So brent i can tell if its worthd doing it. I suspect its going to be a night and day diffrence for me. When pulling it appart clumps of oil dirt and crap fell out, it was way overdue.

My bikes RUN but ive never touched any suspension before. Its all a first for me.

You've noticed the fast rebound before right? First ride on my 350 the rebound was so fast I thought i had no valving at all. Let me know how it goes.

[Black Sheep]

First ride on my 350 the rebound was so fast I thought i had no valving at all. Let me know how it goes.


thats because there is no valving. the oil is the damping. the reason behind the fast rebound is in the spring rates and oil weight which determines your damping and rebound. welding the hole on the damping rod is almost the same as going to a heavier weight oil. the problem with this is on hard hits or fast compression you will experiance hydrolic lock. meaning the oil can not go through the hole as fast as it needs to therefore it "locks" up. this is really a band aid cure for a bigger problem.

the first step in fixing 350X forks is heavier oil and more of it. the next step is springs, then damping rods.

[NOS_350X]

I did it AND went to a 10wt oil huge diffrence when i jump up and down on it (just sitting there) but when i rode it not much diffrence :( ill see when i get on some non snow covered areas where i can actualy use the suspension.

[Black Sheep]

if you weigh over 150lbs and are not running 15wt oil your oil is too light for a 350X

[NOS_350X]

well i was about 120, until a few months ago, now im right at 150 lbs

[Black Sheep]

digging out my old black book and looking at my 350X fork settings throughout my testing 350X's here is what i have done and what i ended up with.

stock forks run 290cc 7.5 weight oil which gives you a oil level with the springs out and forks collapsed of 8.5"

this setting is almost always to soft and rebounds to fast.

my first change was to go up to 10wt. oil at 5.5" from top or aprox 360cc. this is good for causual trail riding for riders over 150

this helped the stock forks but still lacked in agressive riding.

the next step was to add progressive springs and up to 15wt oil at 7.5" from the top. this is good for heavier or faster riders

the final step was to add terry fork damping rods. this is the ultimate 350X fork. if you still arn't happy go to 85/86 250R forks. but you'll lose turning radius

this was done in 85 and 86. in 20 yrs i never found a better setting. i've tried different variations of the above but always went back to my last one.

since terry damping rods were no longer avalible after 92 i started to use 83/84 250R damping rods which are almost identical to the terry kits. i would often have more then 1 350X other then my original one from 85 with the terry rods. i would install the R rods and they were very similar in action. the only differance was i'd add 1" of oil to the forks with the R rods.

this set up is very competative with the stock suspension on the newer sport quads (not the 450's)

[NOS_350X]

I am really trying to get the things set good. I dont do alot of jumping anymore if any (thank you Craig, Doc and Dirtdog) Im really going to try some diffrent setting to see what works best. I have 4 X's and one with the R forks. I figure i can try all diffrent setting and see what actualy works the best. I also just got a 97cr125 and they have the upside down forks i do want to try them on there.

Very good info in this thread.

My oppinion is,
suspension is a major part that most neglect. Just draining your oil and changing the weight to something that you think might work better for you is a HUGE start. The new smaller hole is an easy mod, and wont hurt anything. If you think you can do it go for it.

Black, can you still get progressive springs? and where?

[dovesprings250R]

Thanks guys. Great info. Diving into mine on sunday.

[Black Sheep]

Black, can you still get progressive springs? and where?


yes they are still avalible. you can try denns kirk or progressive suspension themselves
http://www.progressivesuspension.com/ http://www.progressivesuspension.com/prodSearchResults.aspx?yearID=1985&makeID=32&modelID=308

I can also shed more light on the 3wheel mag artical. as said before this mod will cause hydrolic lock on big hits (not just jumps but in fast g out situations) 3wheel magazine would later remove there modified damping rods and replace them with terry rods. The mod they did was a temporary fix untill something better came along.


Nick, if you do go with progressive springs you will need to make a pre load spacer. PVC works good just don't go bigger then 2"

I've done more fork mods for 350X owners then any other mod and every one had these springs installed. 50% had the damping rods as well. No one ever chose the weld/smaller hole option.

[mywifeknowseverythin]

Nick, if you do go with progressive springs you will need to make a pre load spacer. PVC works good just don't go bigger then 2"

I have a set of Progressive Springs....They come with the PVC

[Black Sheep]

I have a set of Progressive Springs....They come with the PVC


i know they do but you can adjust your pre load by its length. for heavier or harder riders i usually go with 1 3/4" lesser demands i would go to 1 1/2" flat track i would go with 1 1/4" (almost no preload)

i've also seen people throw the PVC away and use steel...

[dovesprings250R]

How hard to put 250R forks on the 350x. just curious?

[Black Sheep]

How hard to put 250R forks on the 350x. just curious?

depends what year R your talking about


on 85/86 you will have to use the R's tripple clamps and in order to do that you have to remove the R steering stem from the R clamps Then the hole will have to be bored out to accept the larger X stem.

for 83/84 R forks just swap the lower R legs for lower X legs

[dovesprings250R]

The 83 84 R fork thing sounds neat. I can get a good set real cheap. I'll try more and thicker oil to start.

[Black Sheep]

I'll try more and thicker oil to start.


how much do you weigh???

[dovesprings250R]

150 pounds. I ride hard, espcially in rough terrain and whoops. Not much jumping but sometimes.

[Black Sheep]

if your running sock springs i would start with 15wt at 6" from top with the springs out and the tubes collapsed. when filling the forks with oil place your hand over the opening and pump up and down severall times. you will feel pressure building up. this will bleed the air from the fork.

[dovesprings250R]

Did my forks today. I ended up not welding the hole and going with the 15wt oil at 6 inches from the top compressed as blacksheep recomended. Seems to have worked. Re bound is slower now but I'll have to ride it at the rally to really feel it. I plan on making thse forks as nice as I can.
Thanks to Nick and Blacksheep for help with this one!

[dovesprings250R]

well, the 15 wt oil 6 inches from the top did the trick! rebound is slowed to an acceptable level, it no longer tos out, it hits the whoops way better and allows much faster riding. Thanks blacksheep for the tip. It got ridden lots and hard at the trike rally at rasor road.

[Black Sheep]

Thanks blacksheep for the tip.

no problem, glad it worked out for you.



I plan on making thse forks as nice as I can.

stay tuned to the ultimate 350X build. I will do a complete write up on the forks.

[likestrikes]

Do you have to use the 350X stem in the 85/86 250R tripple clamps? Or can you change the races in the 350X frame and run the entire R assembley with the tapered bearings in the 350X headset.

In other words, can I buy a 250R allballs kit, use 85/86 250R forks and tripples and insall that in a stock 350X frame if the outer races are knocked out?

[Black Sheep]

Do you have to use the 350X stem in the 85/86 250R tripple clamps? Or can you change the races in the 350X frame and run the entire R assembley with the tapered bearings in the 350X headset.

In other words, can I buy a 250R allballs kit, use 85/86 250R forks and tripples and insall that in a stock 350X frame if the outer races are knocked out?

you have to swap the steering stem from the 350X and install it in the 250R tripples. you will need to bore out the 250R tripples to accept the larger 350X stem.

[likestrikes]

Well, I have a mill so I can do that...

Whats the issue? Is the head tube on the X different in diameter or length than the 250R?

Thanks for the help................

[Black Sheep]

the 250r head tube has a 47mm inside diameter while the 350X is 3mm larger at 50mm.

the 350X stem has a larger diameter as well

[Dammit!]

How many ounces of fork oil do I need to purchase so I can run 15 weight 6 inches from the top as dovesprings250r did? I rode his 350x at the trike rally right after he made that change and his forks felt WAY better than mine. Mine are so springy I wouldn't be surprised if there's no oil in them at all (I haven't checked since I bought it, lol).

[Black Sheep]

I never kept track of the amount in ounces. Its not a accurate way to measure as you always have residual oil left in your "ratio rite" cup. as little as one drop can raise the oil level by 1mm.

If you get two bottles you'll have more than enough.

[likestrikes]

Yep, 2 bottles will do it and I used 15wt BelRay.

It is a nice upgrade, I did mine based on everything from Bill, best part about it is getting the forks apart, cleaned and replacing any bushings that are worn and the seals. I also replaced the damping rings as they are cheap but can be brittle.

Only thing is now I have upper and lower 84 250R parts that are useless to me!!

I just measure it out the best I can but I do check it with a 12" machinists ruler with the forks collapsed. I'm no racer but I try to get things the best I can anyhow :D

DC

[Dammit!]

Forgot to post back with the results.

I replaced my fork oil with 15wt Maxima fork oil right before the last Glamis ride. 6 inches from the top like dovesprings did. Worked out really well. No more ridiculously fast rebound. Makes the whole trike feel more solid.

The only problem I had (if you could even call it a problem) was getting the oil level exactly right. I used a screwdriver marked off with black ink at the level I wanted but the new oil was so clean I couldn't see it. :lmao: My eyes are getting bad and I did it in the evening with just the garage lights so that didn't help at all. Michelle made me a dipstick out of white carboard which was a hell of a lot easier to see. :D

Anyway, thumbs up for such a simple little change.

P.S. Thanks Bill for the hook up!

[NOS_350X]

A good easy way to get the level right, over fill it, Get a syringe(SP?) with a hose the right length. Drop it down to the right depth, and suck out the excess,