CRF50 HD clutch springs pop the front end shifting into second

I picked up a CRF50 over the weekend, previous owner put in stiffer clutch springs (not sure which brand). When I shift to second going anything faster than a crawl the front end pops up hard, I have to put all my weight forward to avoid it and almost spun out a few times. I'm 185 pounds, its got stiffer +1" fork springs and stiffer rear spring so the bike seems to be handling my weight just fine aside from the shifting pop.

Is this normal?

Does the engine return to idle when you let off the throttle to shift? if not i would check that out first. it may stay high enough to keep the centrifugal clutch engaged.

you can also try adjusting the clutch.

Does the engine return to idle when you let off the throttle to shift? if not i would check that out first. it may stay high enough to keep the centrifugal clutch engaged.

you can also try adjusting the clutch.

I only have my CRF230F to compare it to , only other bike I've ridden. But it acts like the 230 does if I let off the gas without pulling the clutch, decelerates.

That video is awesome, I'll check it tonight, thanks.

If the engine isn't returning to idle what is the remedy?

i'm pretty new to this but normally it means you have an air leak somewhere. some one will probably chime in to either confirm or correct me. (hopefully) plus they can give you a more precise location of the air leak. i want to say its at the intake manifold.

Okay, sorry to took so long to respond, tonight was the first chance I had to mess with it so thanks for the replies.

I tried the clutch adjustment showed in the youtube link. That seemed to be part of it, now it definitely stays disengaged while the shift lever is help up. But as soon as I let off the lever it still bucks and now I can hear that its not returning to idle.

So I did some more looking at the bike and discovered a few things the previous owner had done that he either forgot to tell me or decided not to for some reason.

Intake/Exhaust mods appear to be:

(From what I can tell the carb and pipe are stock)

-air box removed with Uni type filter

-choke mod with plug

-stock spark arrestor/end cap has the mesh cut out

I have no idea if the jetting was ever changed or if anything else was done internally but the engine exterior is stock.

My main purpose for this bike is to ride in the backyard and we have bitchy neighbors. I'm hoping to keep it as quiet as possible which is why I wanted one with the stock engine and pipe, although I could tell right away it wasn't as quiet as stock. I know getting a new spark arrestor would quiet it down a bit but will it end up messing with the back pressure? I thought I read the baffle mod works best with the spark arrestor intact, maybe I'm wrong.

I've attached some pics, maybe someone will see something I don't since I'm real new to all this and trying to learn as I go. I see some gunk on the right side of the carb, maybe something leaking there?

Are any of the open ports on the carb supposed to have anything attached that would be causing an air leak or should I me looking somewhere else? (breather tube, etc)

right side

30bdxci.jpg

left side

1g53yt.jpg

closeup on top of carb, the rubber boot on the carb cap is rotted out, could that be the air leak source?

a0b4fd.jpg

Edited by mediaoffline

not sure whats going on with your bike. Like i said im kind of a noob too. The stain i would assume is from some one unscrewing the fuel screw and gas leaking and never being wiped off. then it varnished the outside of the carb. (better the outside than the inside i guess) the fuel screw looks like its turned way out in the pic. is it borderline falling out?

it may just be a lean condition with all the mods. that would explain the fuel screw being out so far. someone was trying to correct it without changing jets. (unless on a 50 its an air screw then im completely backwards and you should ignore me)

the fuel screw looks like its turned way out in the pic. is it borderline falling out?

To be honest I have no idea, never messed with carbs before but hopefully this weekend I can take mine apart and clean the inside while I learn about it.

Thanks for your help :smirk:

the carb on the 50 is super easy to work with. maybe with our two noob brains working on it we can figure it out. im wondering if no one else has chimed in because they are waiting to see how long it takes us to figure this out. lol.

Try setting up a baseline to work from and return to, when making adjustments. Set the air screw OUT to 1-3/4 turns from seated, put the jet needle clip in the 3rd (middle) notch, and go from there. If there is a slight hesitation when rolling on the throttle, turn the air screw IN a 1/4-turn to richen it and see what happens. If there is a sputter in the midrange while holding the throttle steady, try lowering the clip one notch (4th from top), to richen it. If it stammers in the high RPM range, you might need to go up one size on the main jet.

The idea behind the baseline is to give you a setting to return to if your adjustments don't work, and to try again.

Testing for an air leak is a matter of spraying some contact cleaner on the manifold/head area, and also the manifold/carb area while the bike is running, and see if there is a marked increase or decrease in the RPM level, and then a return to the previous level. The level change indicates an air leak.

Alright, took off the carb, cleaned everything, blew it all out with compressed air and reset everything based on dirtbkr188's recommendations. To my surprise it only needed some small adjustments to the air and idle screws to get it purring, even moved the clip back to the 3rd position (it was 2nd from the top before, I guess the air & idle screws were backed so far out to compensate for that). I felt no sputtering and no real bog although it didn't feel like the power was quite as strong in the midrange, may have just been in my head but either way the bike at least sounded and idled right.

However, no change in the 1st to 2nd gear wheelie pop. Upon more testing the throttle doesn't apear to be sticking. 2nd to 3rd is pretty darn smooth so I'm thinking maybe the 2nd gear pop is just the way it is. I've been adjusting my riding style, shifting to second almost immediately. And if my takeoff speed isn't important I just keep it in 2nd. I noticed the rear sprocket is a Two Brothers 37t but from what I can tell that's the stock size so that wouldn't change anything.

So maybe there was no answer after all. Would the HD clutch springs loosen up over time? I know the guy I got it from only put almost no miles on it so maybe they're not stretched out yet?

Either way, thanks for all the help guys :smirk:

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