CBR250 Forums banner
1 - 19 of 19 Posts

·
Registered
Joined
·
96 Posts
Discussion Starter · #1 ·
Hi all

decided to give the bike a bit of a service the other week. Changed the oil, oil filter, spark plugs, and took the carbs out and gave them a good clean.

Everything seemed to go ok. Put the carbs back in and the bike started after a couple of tries. Took it out for a spin and all seemed good. Took in out for a ride last night and relized that the bike was heating up way to quick and after sitting at a traffic light for almost a minute the needle would jump to over half way in a blink of an eye. And it was pretty cold last night in Sydney. It never used to be like that before the service. The fan does kick it so I assume the thermostat is working but it seems to struggle to keep up. Only once you reall. Take off does it start to cool a bit. Also when I stop and The lights and let it idle for a bit it turns off. I have no trouble turning it bavk on. Starts first go. And I also found the idle starting to play up as well. It will drop from 1600 to 500-600 for a few seconds then creep back up and I'm not getting much power out of it. Ohh and also the bike seems to not like the choke much. If I try to use it, the bike either turns off or struggles.

A shot in the dark would say that the idle and choke issues would be the carbs need balancing?? Please correct me as my bike knowledge isn't great.

But the overheating issue has got me stuck. No idea what it could be. I'm also worried as i'm getting a knocking sound from the engine also. I hope I haven't overheated the internals and fried something......

Please guys, any advice or theories?
 

·
Registered
Joined
·
54 Posts
As Aj26 said

Did u cheak to make sure your carb boots were ok and that the carbs are sealing. sounds to me like a leaking carb boot causing the idle to jump up and down also could cause the high temps while stopped

Correct me if im wrong but would that also cause the engine to run lean?


I'm just a n00b don't take my word but would like to no if I'm right : )
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #4 ·
aj26 said:
When was the last time you fully flushed out the old coolant and replaced it with new coolant?
I've only owned the bike for 3 months so not sure when it was last done. Either way Ill give that a shot. I'll change it tomorrow[hr]
Nathan89 said:
As Aj26 said

Did u cheak to make sure your carb boots were ok and that the carbs are sealing. sounds to me like a leaking carb boot causing the idle to jump up and down also could cause the high temps while stopped

Correct me if im wrong but would that also cause the engine to run lean?


I'm just a n00b don't take my word but would like to no if I'm right : )
I'm not too sure but it sounds likely. Off come the carbs again tomorrow but I might have to take them somewhere to get them tested. It was my first carb clean and don't really know much on testing them in any way. I'm thinking a compression test might me a good idea as well....
 

·
Registered
Joined
·
7,411 Posts
Sounds like its running lean to me, mine was running ridiculously hot when it was lean.
Wouldn't hurt to do the coolant but id inspect your carb boots first to save needless work (take the metal tightener rings off and check for splits or cracks under them), did you touch the pilot screws at all while cleaning the carbs?
If your boots are fine does it have enough oil in it?
If it does try giving your pilot screws 1/8th to 1/4 a turn out to rich the mix up a bit.
In the mean time dont rev the fuck out of it or give it more than half throttle til you've fixed the problem, high revs and lots of throttle while running lean can be nasty for your engine.
 

·
Registered
Joined
·
4,388 Posts
Flush out your coolant before moving on to anything else.
Check your wiring harnesses that is going to the instrument cluster, it could be someone loose and making the fan not turn on.

If your want you can also install a fan switch, just incase your fan doesn't turn on you can bypass it
http://cbr250.com/forum/thread-292.html

Don't touch your carbs if you don't know what your doing. Risk creating more problems with trying to start the bike
 

·
Registered
Joined
·
7,411 Posts
He rekons his fan is working.
Also if the problem suddenly cropped up after a carb clean i seriously doubt its a sudden coolant problem, thats the last thing I'd be doing if i had a checklist.
Carb boots and pilot screws are likely culprits IMO
Coolant has ZERO effect on idle hunt to BTW
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #8 ·
:popcorn:
Aduro said:
He rekons his fan is working.
Also if the problem suddenly cropped up after a carb clean i seriously doubt its a sudden coolant problem, thats the last thing I'd be doing if i had a checklist.
Carb boots and pilot screws are likely culprits IMO
Coolant has ZERO effect on idle hunt to BTW
yeh the fan is working and thermo is opening up. Oil is clean and coolant is clean so it's not a head gasket. I made a switch for the fan by haven't installed it yet. I'd rather not take the easy way out. I'd prefer to fix the problem. Most likely it's something to do with the carbys. I think I'm just going to pull them out and take them to a mehanic. I'm not too confident on working on them. Cleaning them is one thing but I don't want to try adjusting or working on them any further. Worried I'd cause more damage.....
 

·
Registered
Joined
·
7,411 Posts
robbie said:
:popcorn:
Aduro said:
He rekons his fan is working.
Also if the problem suddenly cropped up after a carb clean i seriously doubt its a sudden coolant problem, thats the last thing I'd be doing if i had a checklist.
Carb boots and pilot screws are likely culprits IMO
Coolant has ZERO effect on idle hunt to BTW
yeh the fan is working and thermo is opening up. Oil is clean and coolant is clean so it's not a head gasket. I made a switch for the fan by haven't installed it yet. I'd rather not take the easy way out. I'd prefer to fix the problem. Most likely it's something to do with the carbys. I think I'm just going to pull them out and take them to a mehanic. I'm not too confident on working on them. Cleaning them is one thing but I don't want to try adjusting or working on them any further. Worried I'd cause more damage.....
Mate try turning your pilot screws that quarter turn out first, you wont damage the carbs by doing this. Im quite sure this will fix it if its running lean, if it doesnt then take the bike to a mech but try and save yourself some cash first. Alternatively drop by the Ryde area tmoz arvo after i get back from the Old Pac run and ill take a quick geeze for you.
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #10 ·
Aduro said:
robbie said:
:popcorn:
Aduro said:
He rekons his fan is working.
Also if the problem suddenly cropped up after a carb clean i seriously doubt its a sudden coolant problem, thats the last thing I'd be doing if i had a checklist.
Carb boots and pilot screws are likely culprits IMO
Coolant has ZERO effect on idle hunt to BTW
yeh the fan is working and thermo is opening up. Oil is clean and coolant is clean so it's not a head gasket. I made a switch for the fan by haven't installed it yet. I'd rather not take the easy way out. I'd prefer to fix the problem. Most likely it's something to do with the carbys. I think I'm just going to pull them out and take them to a mehanic. I'm not too confident on working on them. Cleaning them is one thing but I don't want to try adjusting or working on them any further. Worried I'd cause more damage.....
Mate try turning your pilot screws that quarter turn out first, you wont damage the carbs by doing this. Im quite sure this will fix it if its running lean, if it doesnt then take the bike to a mech but try and save yourself some cash first. Alternatively drop by the Ryde area tmoz arvo after i get back from the Old Pac run and ill take a quick geeze for you.
no worries I'll try that and see how it goes. Was it a quaRter turn clock wise or anti clock wise?

Where abouts in ryde are you? I work at west ryde. Actually at work now but I didn't ride to work. Too cold tonight
 

·
Registered
Joined
·
7,411 Posts
Near the golf course. you want to to turn them out so that would be anti-clockwise.
Pilot screws are responsible for idle and low rev fuel/air mix. turning them in allows less fuel turning them out allows more. If your bike is running lean and you haven't changed your intake (High-flow filter or altered air box) or your exhaust then changing your pilot screw settings usually remedies it.

I put a clean air filter in mine after changing carby boots awhile ago and it was running massively hot and seemed to have a bit less power. Didnt get around to fixing it for ages and the radiator boiled over. turned my pilot screws out and it cleared right up.
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #12 ·
Aduro said:
Near the golf course. you want to to turn them out so that would be anti-clockwise.
Pilot screws are responsible for idle and low rev fuel/air mix. turning them in allows less fuel turning them out allows more. If your bike is running lean and you haven't changed your intake (High-flow filter or altered air box) or your exhaust then changing your pilot screw settings usually remedies it.

I put a clean air filter in mine after changing carby boots awhile ago and it was running massively hot and seemed to have a bit less power. Didnt get around to fixing it for ages and the radiator boiled over. turned my pilot screws out and it cleared right up.
ok so i took the carbs back out today and turned the pilot screws 1/4 of a turn. ive attached a video of the outcome. havent taken it for a ride yet but still doesnt seem good. the idle is still playing up. if you give it a rev it sits fine fr about a minute then starts to bounce around again.

not sure why the video is upside down but im sure you can get the idea of whats happening. also added audio file to show the engine noise im getting and the ticking sound. not sure what thats from.

http://www.megaupload.com/?d=QKEH25XI
http://www.megaupload.com/?d=1N7MW1BQ

tried to add them as atachments but it didnt work. so i uploaded them.
 

·
Registered
Joined
·
7,411 Posts
My net is way to slow to watch the videos :(
Did you check the quality of your carb boots while you were there?
When i had a leak in one of my boots there was a really quick hiss sound that almost sounded like a tick which was air getting sucked past the crappy seal made by the dodgy boot every time the cylinder sucked in.
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #15 ·
Aduro said:
My net is way to slow to watch the videos :(
Did you check the quality of your carb boots while you were there?
When i had a leak in one of my boots there was a really quick hiss sound that almost sounded like a tick which was air getting sucked past the crappy seal made by the dodgy boot every time the cylinder sucked in.
yeh the carb boots seemed ok when I checked them. I might try turning the pilot screws 1/8 of a turn more and see if that fixes the problem. Maybe it's still running lean
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #16 ·
Ok so I took the carbs back out and turned it 1/4 turn more. And the 1/8 of a turn for extra measure. The bike runs alot better now and isn't heating up as much as before. And it is responding to the throttle alot better and is running smoother and quicker. But if I let it sit and idle for about 30 seconds after the bike is warm it turns off. Does it mean uts running rich now? Should I maybe turn the 1/8 turn back in??
 

·
Registered
Joined
·
7,411 Posts
Yeah might have been a tad much, and to be honest messing with pilot screws is guess and measure, repeat at best.
Give em 1/8 a turn back out.

General rule: bike warm sitting in neutral, give it a quick rev up and shut the throttle back closed. If the revs hang and don't drop straight back to idle (1300-1700rpm) your probably running lean. If the revs drop below idle and struggle back up or stall completely then your probably running rich.
Just keep fucking with it making MINOR changes and you should work it out eventually if that's your only problem.
Is it still hunting for idle?
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #18 ·
Aduro said:
Yeah might have been a tad much, and to be honest messing with pilot screws is guess and measure, repeat at best.
Give em 1/8 a turn back out.

General rule: bike warm sitting in neutral, give it a quick rev up and shut the throttle back closed. If the revs hang and don't drop straight back to idle (1300-1700rpm) your probably running lean. If the revs drop below idle and struggle back up or stall completely then your probably running rich.
Just keep fucking with it making MINOR changes and you should work it out eventually if that's your only problem.
Is it still hunting for idle?
Yeh I'll keep going at it 1/8 of a turn at a time. Still hunting a little but not as much as before. It's barely noticeable now.[hr]
robbie said:
Aduro said:
Yeah might have been a tad much, and to be honest messing with pilot screws is guess and measure, repeat at best.
Give em 1/8 a turn back out.

General rule: bike warm sitting in neutral, give it a quick rev up and shut the throttle back closed. If the revs hang and don't drop straight back to idle (1300-1700rpm) your probably running lean. If the revs drop below idle and struggle back up or stall completely then your probably running rich.
Just keep fucking with it making MINOR changes and you should work it out eventually if that's your only problem.
Is it still hunting for idle?
Yeh I'll keep going at it 1/8 of a turn at a time. Still hunting a little but not as much as before. It's barely noticeable now.
it's a pain in the arse bolting the carbs in and the air box and filter and tank then taking them back out again and again..... But it has to be done I guess. I tried what you said with the bike warm and gave it a rev. The revs didn't hold at high revs. Dropped down to just under 1000rpm then slowly crept back up to 1500 then after bout 30 seconds it turns off
 

·
Registered
Joined
·
7,411 Posts
Sounds bit rich. when i did mine i left the air box on with the bolt that holds the lower box tot he frame off and just tightened/ loosened my boots to take the whole lot off and adjust the screws with a stubby screwdriver.
 
1 - 19 of 19 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top