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New Member with a carb question (I think) - Vid

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billy_b

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Discussion starter · #1 ·
Hi all, I stumbled onto this forum while searching for a solution to a problem with a bone stock crf50. I had no idea these bikes had such a big following, looks like you could get caught up real real easy!!

Anyway I bought the bike for my kid, the last owner said it was running fine when put away. The issue is it has an rpm hang when you release the throttle and it will bog a bit when you blip the throttle. I wont put my kid on it until I sort the issues as I dont want him to get scared or worse hurt if the bike does not stop when he releases the throttle. Below are the items that I have already checked:

-Lube throttle cable and check routing
-Visually inspect throttle barrel return (snaps back quick)
-Check for air leaks
-Adjust air/fuel (maybe adjust is the wrong word - mess with is prob more accurate)
-Remove float bowl, visually inspect and clean out main jet

When I had the carb apart one thing that I could not do was to ream out the pilot jet (I did not have a wire thin enough). My question is should I be able to do so? Does anyone feel this may be the issue (the carb was pretty clean when I took it apart)? In addition the motor will also hunt around if I let it sit and idle and it is acting a bit weird with the choke setting (revving when shutting the choke on a warm motor). I added a youtube link of the bike running if anyone thinks it would help in diagnosing. I am not afraid to start taking stuff apart I just dont like trying to force stuff when I dont know the way its supposed to work. Thanks in advance for any opinions!

Vid

 
#2 ·
Stock carb pilot is near impossible to clean out. If you cleaned all the ports, jet(s), and everything else play with the idle screw and see if you can clean it up. The needle position could need to be changed.
 
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#3 · (Edited)
You may have an air leak between the carb and the manifold , the O ring might be beat or crushed and air is getting past it ..you could spray some carb cleaning in the areas where the manifold meets the carb and motor to see if you get any changes when the bike is idling .
Also try the fuel petcock lever facing with the lever down to On instead of pointing up as I see it in the video .
Your petcock could be clogged.i have found that when I turn my sons xr50 to off thebike will run like yours does as I feel I'm cutting off some pressurized fuel flow.air going to the carb ..if your petcock is clogged or does. It like. Ring on reserve may e it's causing the issue .make sure the tank is atleast 3/4 full of gas and the cap is not creating a vacuum lock
 
#4 · (Edited)
Make sure your fuel petcock is not clogged and is flowing gas clearly as if it's not filling the carb right with fuel the carbs bowl is going to be playing catch up and you may get a blip in throttle when the bike seeks fuel ..but with a clogged or slow dripping fuel petcock the bowls going to run out of needed gas to run correctly

When I was a kid with z50s/SL70s O had more trouble with clogged fuel percocks then anything .small flow holes in the petcock the smallest debri or old caked gas of clog it . Or inner fuel tank filter being caked up with old gas .
 
#6 ·
IMO, the above answers are over complicated.
Todays gas is horrible. It has sooo much filler/cut in it, that when the actuall gas evaporates away inside the carburetor, the filler/cut is left behind.
Then when you start it up, after the gas evaporated out of the carburetor and only the filler/cut is left behind... The filler/cut gets sucked up into the jets in the carburetor. On a bike this small, the jets ( jets= a measured size hole that only allows X amount of fuel to enter engine ) can become clogged very quickly. Very simular to how Cholesterol causes a heart attack.

Anyway when you blip the throttle, you are giving it a big gulp of air, and because the jets are partially or completely clogged, not enough fuel is presiant, so you get the "bog". Also a common lean condition is added time for rpm's to come down after high rpm's.

IMO, I would remove carb, and just replace the pilot jet with a new one of the same size.


Hope that helps. Feel free to PM me or ask me here on the thread if you have any questions or I was t clear about something.
 
#7 · (Edited)
billy_b said:
Thanks for the replies, I will try the petcock and check the flow rate and report back.
Click to expand...
I had this problem with my XR50/88..the petcock was clogged as the bike sat with old gas in a cold garage for what may have been a year... or two(before I bought it)
When the seller tried to start a bike that always ran it would not run right..His first thought was old gas,We pulled the fuel line from the petcock going to the carb off (easy to do) and leaned the bike over,turn the petcock to on and nothing..Shaking the tank provided a slow drip.. I cleaned the tank out like giving it an inner bath with new gas a few times and the flow cleared,the bike ran perfectly at the track after that...later at home I blew out the petcock and checked the carb bowl,jets to be sure no blockage..Yet my next step was to go with checking clogged jets but too many times in the past I wasted hours/time pulling off carbs before making sure I was actually getting proper flow of fuel to the carb..Today he first thing I do when a bike is running funny is make sure I’m getting a clear flow of non restricted fuel,also checking for a vacuum lock in the tanks cap..

This may not be your problem but it’s good thing to know first that you are actually getting enough gas to the carb ..


I agree with what Jordo says Todays gas is horrible. Check those Jets..replace it.

.................................................. .

I also feel that if a bike has ran perfectly before you got it then no major changes need to be made to settings,settings should be left alone unless they were messed with upon trying to get a bike to run,thus if a bike is stock set back to factory settings and adjust from there,after cleaning the carb......If the bike ran before and sat for awhile with fuel in it then the answer is Fuel Issue,old gas,..Clogged carb jets..Clean the jets,if he bike is not running right set idle mixture screw back to factory setting if the bike is stock and set from there..Smetimes upon messin with the stock bikes you get way out of whack with changes,headaching,start from factory stock settings and go from there.


I have found it really tough to clean the Stock carb pilot(sons XR50) ,I had a carb where the fuel shellacked in the Stock carb pilot and after soaking the carb in gas,carb cleaner,high pressure air the old gas is like glue in Stock carb pilot..The old gas just keeps flaking out ..
The problem you are having does sound like this pilio jet is clooged up inside..
Funny I was looking on youtube and found this video


Thanks man. I figured it out. Basically the pilot jet is nonremovable and it was clogged really badly. I had to really get in there and clean everything out. I also got the tool to adjust the air/fuel screw finally. I have it tuned pretty well now.





..............

....My only answer with the clogged pilot with a race coming up fast was to seek out a used OEM carb on ebay(or here) and try it.I will admit I got lucky finding the carb I did on ebay cheap as it as taken off a bike that was being upgraded so the carb was spotless inside..
I was easy as pie to just throw on another carb..but I’m still working on getting all that shellacked fuel out of that old carbs pilot jet


What I like about my tb88(XR50) with 20mm carb is it has no bog..if I blip that throttle it revs perfectly....I really was the best thing about the bike when I bought it.
 
Discussion starter · #8 ·
I didnt have time to get into it yesterday as work has been nuts. I might not get the chance until the weekend. All great advice for sure. I will start with the easy stuff outlined - my suspicion was the pilot but i didnt want to mess anything up before I knew more about it. I will def post the results after I try a few.
 
Discussion starter · #9 · (Edited)
OK I had a bit of time to look at things yesterday and have a bit more info. I took the carb off again i tried to pass a wire through the pilot jet but even with the smallest diameter i could not get through but I dont think its a blockage it just seems that it maybe is not a straight shot or something?

When I spray some cleaner through the pilot hole on the throat of the carb I do see some come out the pilot jet so I know its not totally blocked off. Also as you can see in the pics the carb was really clean to begin with - I honestly dont feel its a blockage but it would be great if someone could confirm that I should not be able to pass a wire directly up the jet itself.

I tested the fuel flow and it seems fine. What I did notice is if I turn the mixture screw all the way in the bike runs way better. No rpm hang and a fairly crisp response to throttle. I dd test for leaks with my torch but now I am second guessing. Maybe the o-ring is leaky on the carb or intake side of the isolator as some have suggested earlier?

Link to the pics --> https://plus.google.com/photos/107271227181792324762/albums/5845141719765373857. The one pic that says pilot jet is where i sprayed cleaner in to ensure it came out the other side.
 
#10 · (Edited)
billy_b said:
OK I had a bit of time to look at things yesterday and have a bit more info. I took the carb off again i tried to pass a wire through the pilot jet but even with the smallest diameter i could not get through but I dont think its a blockage it just seems that it maybe is not a straight shot or something?

When I spray some cleaner through the pilot hole on the throat of the carb I do see some come out the pilot jet so I know its not totally blocked off. Also as you can see in the pics the carb was really clean to begin with - I honestly dont feel its a blockage but it would be great if someone could confirm that I should not be able to pass a wire directly up the jet itself.

I tested the fuel flow and it seems fine. What I did notice is if I turn the mixture screw all the way in the bike runs way better. No rpm hang and a fairly crisp response to throttle. I dd test for leaks with my torch but now I am second guessing. Maybe the o-ring is leaky on the carb or intake side of the isolator as some have suggested earlier?

Link to the pics --> https://plus.google.com/photos/107271227181792324762/albums/5845141719765373857. The one pic that says pilot jet is where i sprayed cleaner in to ensure it came out the other side.
Click to expand...
As far as "I' know you can't pass a wire through the pilot jet..at least every wire I tried(garbage bag tie) I have not been able to get a straight shot through..

(I need a verification on this if it's not a straight shot through)








There could be some crud high up in the pilot jet..



I'd suggest to change the 0 ring anyway..I was able to find the OEM 0 ring on eBay cheap ..Later I bought a whole kit at my local Motorcycle mall to have spare parts..It's cheap
to buy..

Check here for parts number...I searched 2004 CRF50
2004 Honda CRF50F OEM Carburetor | MotoSport





UGH..
The spot where you are at with the bike right now I’ve been at with an XR50..
But I don’t know what for sure thing I did to fix the problem..

I can tell you all the things I did..
Checked for fuel flow.,petcock,fuel line,cap,tank
New Gas
New Spark Plug
Made sure throttle and cable wasn’t sticking and free.
Cleaned Carb several times/removed-cleaned removable jets..
Set Carb back Factory Setting,making sure throttle needle was at factory setting.(middle)

Checked for Air leaks
Changed 0 Ring..(gasket ,o ring kit

Removed Air Filter (it was caked in oil and dirt) cleaned and re oiled..(making sure to put air box Ground wire back on)
Checked carb fuel overflow line to make sure it was not crimped,closing air off that flows back into carb.

After all that,bikes fixed..
 
#11 ·
Alcohol, which is found in E-10 pump fuel, is hygroscopic. Fuel left in the float bowl for extended periods will attract moisture from the air causing corrosion and blockage of the brass jets.

Had the same problem as you with my kids CRF50. Took the carb off and soaked it in carb cleaner (some people use Pine-Sol) then blew compressed air through all the jets and orifices.

Put the carb back together and after some minor air screw adjustments it was working like new.

Two things about the CRF50 with a stock carb:

1. These bikes are cold blooded so make sure it's fully warmed up before tuning with the air screw.

2. If its going to sit longer than 2 weeks, drain the float bowl.

A sticky throttle is usually due to a bad throttle cable. Just replace the cable.
 
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