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CRF150R forks, bottoming out

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I have CRF150R forks on my 230F. I rebuilt them with new seals, oil, and springs. Right now I have the compression damping on the stiffest setting but still bottom out when landing jumps. 

I want to adjust the air space in the forks as my next tweak before going for stiffer springs. Should I add oil or remove oil to improve the bottoming resistance of the fork? What kind of gap should I be going for?

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Like Brother said ADD OIL 10cc at a time. If that does not work 5wt oil then .40 spring. What is your rebound set at?  We run CR85 fork  oil 4in from top zero bottom out.

Edited by bajatrailrider
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Just now, bajatrailrider said:

When it bottoms out do you hear metal to metal?  Like I did.

Nope, just hits the fender. I haven't machined the little bosses off of the CRF150R bottom triple yet to raise the fender, but it will only bring it up about 3/8" of an inch which I don't think will do much.

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I have used CR80 and CRF150R forks on XRs and fender clearance can be an issue with a 21" front wheel. I use a low profile small 21" front tire for extra clearance,  cut the fender mounts . Plus run high oil levels and correct springs. 

You can also push the fork down in the triples up to 1/2" for more fender clearance.

You didn't say where the tire contacts the fender; front/rear/center.

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 I by mistake put Hi profile front tire on,glade I did because it rides plush. No fender rub I must have enough oil in forks to stop that.

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There is no single item that will fix the front tire hitting the fender when putting a 21" wheel on forks designed for smaller wheels, it takes the sum of several small adjustments. So keep working the little details.  I had one fender that was too narrow at the fork tubes and the tire rubbed it before bottoming. :banghead:  I used heat and reshaped the fender. Also when a fork bottoms the lug on the slider does not contact the bottom of the stanchion, it leaves about about 5/8" of the slider exposed.  So while checking fork travel by dirt left on the slider remember the last 5/8" is never used.  

on edit: The forks bottom when the large washer on the underside of the cap contacts the top of the slider.

One adjustment I left out, while not directly related to the above, does provide full suspension travel: The damper rod is screwed into the fork cap and locked with a jam nut.  How far you thread the rod into the cap determines fork rebound limit, e.g. if you screw it in too far you reduce available fork travel. One diameter of thread into the cap provides full rated travel. It also affect spring preload.

Edited by Chuck.
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How does the fork feel/work otherwise?  Damping and spring rate have other jobs and should not be compromised to fix bottoming.

Fork oil level is the proper way to prevent/control bottoming, that's it's only job, IIRC.  I weigh 185lbs and can easily bottom my OE forks with 0.46kg/mm fork springs and the fork oil level too low.

Edited by MetricMuscle
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46 minutes ago, Chuck. said:

There is no single item that will fix the front tire hitting the fender when putting a 21" wheel on forks designed for smaller wheels, it takes the sum of several small adjustments.

Fork oil level would fix the problem but possibly at the cost of less total travel.  

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20 hours ago, MetricMuscle said:

Fork oil level would fix the problem but possibly at the cost of less total travel.  

My susp tuner guy likes to run light wt oil,but run hi oil level for no bottom out. This is in the range of factory spec,he is one of the few guys. That gets it when it comes to trail susp.Most all company's do MX/desert race susp. Even that they say we do it all  far from the truth. Like racetec spring calculator they ask your age/weight/Motocross/trail/Nov/expert. They give you spring rate way too stiff great to beat you to death . Even if you use there guild. Punch in your 125 pounds when your 150 pounds,novice when your intermediate, age 90 when your 20   JAAAA same deal you got a beater.

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On ‎5‎/‎4‎/‎2017 at 11:38 PM, Chuck. said:

I have used CR80 and CRF150R forks on XRs and fender clearance can be an issue with a 21" front wheel. I use a low profile small 21" front tire for extra clearance,  cut the fender mounts . Plus run high oil levels and correct springs. 

You can also push the fork down in the triples up to 1/2" for more fender clearance.

You didn't say where the tire contacts the fender; front/rear/center.

Hey Chuck, might you know if the CRF150R forks are marked with a different series reference on the lower axle lug than the CR80/85 forks?

My CR85RB forks have "GBF" cast on the lug and I'd think the 150R forks would/should have "KSE".  All of the current 150R forks on eBay have "GBF" and I'm just wondering is these are actually drilled CR80/85 forks and not genuine CRF150R forks.

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GBF is on my CR85 & CRF150R lugs, the only difference I could see is the ID of the axle holes. There are a lot of minor differences in other parts of the forks depending on model/year but the lug castings seem to be the same.

GBF, and other 3 character codes, in the middle of Honda part numbers is the Product Code for that part, and it indicates the product that part was designed for. Honda likes to reuse parts which is why a CR80 part is on a CRF150R.

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