[Andy Salmonsen]

Yes we have definitely learned a lot about bikes, i really appreciate the time that Ive had with doing this with my dad.

Today we finally fired the bike up and have a few problems, but here is the low down.

Bike took a while to fire up and was back firing quite a bit. Was finally able to get it going after about 2 min of kicking and it idled well with the choke on, but the second u turned the choke off it would slowly loose revs and then die. As we fiddled with firing it back up we also noticed that the oil was leaking from the oil filter. We fired it up one last time, turned the choke off and i had to keep the bike alive but holding the throttle open just a little bit(We also had the idle as high as it would go). About a minute later of checking everything over on the bike as i held it at i idle i noticed the the header pipe was GLOWING RED HOT, I MEAN ABOUT TO BECOME A PUDDLE OF MOLTEN LAVA HOT!!!!!! I immediately shut the bike down and the redness started to go away but we also noticed smoke coming from the air filter but it only lasted for like 15 seconds.

So yeah a great way to fire your bike up right after a rebuild... so i come to you guys with a few questions.

1. What on earth could cause the header pipe to glow red hot?
2. What would cause smoke to be coming out of the air filter?
3. What could cause the bike to not idle without having the throttle used?
4. What could cause the backfiring?

So if anyone has some answers and advice to my problems lay them on me please... and if someone brings up "buy a 2 stroke kid" I'm gonna go full Liam Nesson on them and i will find them!!! I have to say that this forum and you people have been lifesavers to me and my dad and i can't thank you guys enough!

Thank you

[Aussiecrf230]

I bet your Dad will remember this time with fond memories in years to come too.
Time together is priceless and good for you both.

Well Andy it's all fun and games till the header pipe melts.
So assume you fixed the oil leak because you don't want an oil fire.

1. If the header is super hot after less than a minute then I would suspect it is running lean. Look for air leaks between the carby and the cylinder head.
Getting the boot back on can be difficult sometimes and can be a source of an air leak.
Either that or the carby may have been upside down and some silt out of the float bowl is now blocking the jets. If the carby seems to be the problem look in the idle circuit first. Remember these bikes don't like sitting idling and the header will glow at least dull red normally.

2. Smoke can leave the cylinder when you shut it down if it stops with the inlet valves are open. Check that there is no burning on the aircleaner as a matter of course.

3. Probably answered that in first point.

4. Backfiring, can be as a result of lean mixture or vavle timing out.
Recheck your valve timing as Jim as told you before. it may have jumped a tooth if the tensioner isn't supplying enough to keep the chain engaged.

NOW REPEAT AFTER ME -

THERE IS NOTHING WRONG WITH 2 STROKES.

A lot of us grew up on them and there is nothing like a CR125 to teach you how to ride. Probably because the power was totally outclassed by the suspension.

Look at the length of the post I am turning into Jim, LOL.

You are thanking us by getting in a having a go and learning about your bike.
We all enjoy helping people here at CRFs Only as we are all bike lovers.

[Back2-2]

If you are absolutely certain the timing is correct and not advanced the extremely hot condition sounds like a clogged pilot circuit causing the lean running condition or an air leak in the intake system as Ray stated. You do have coolant in the radiator I hope.
Once that is corrected, the break in should be a short version of what was recommended by the Honda engineers in your service manual. There is probably several opinions here on break-in procedure but as an engineer I tend to believe the engineers that study things tend to know what they are doing. Being an aerospace and mechanical engineer myself here is what I have done for years with great success.
[ There I go sounding like Jim ]
Three heat cycles is the way I have always done it with nothing more than mid throttle with a couple above mid throttle pulls. Heat, cool - repeat three times.
Bottom line -
That's a tough way to start a brand new piston to cylinder break in but the cylinder is technically already broke in so to speak. Look for blockage in the pilot jet for the lean condition before starting the engine again.
Good luck.

[Andy Salmonsen]

Ok, I’ll check the carb as soon as I get the chance today. It probably is a clogged jet because when I was taking everything apart it was the one thing I didn’t really tape up or cover. Will check the clamps and boots again for leaks. I’ll also give the air filter a look over and check timing again.

I’ve got coolant in the bike the only thing that was weird is it says it needs 1 liter of coolant but I could only fill it with .9 liters of coolant, None if the hoses are pinched so I’ll have to see if I can work the air out. I’m also gonna take a look at the oil filter I haven’t been able to do that yet. I did check oil level though with the dip stick and it was same as it was when I put the oil in which is weird to me.

By the way who is this Jim guy who guys keep talking about?

Thanks you guys

[Andy Salmonsen]

One other thing, would the header pipe nuts that lock the header pipe in place cause it to be red hot. I wasn’t able to torque it down all the way to the specified torque and I also didn’t put the silicone to make a seal on it yet, so would those two things cause any of the redness?

[Back2-2]

One other thing I should have mentioned. Use a larger fan to blow across the engine and radiators anytime you are running an air cooled engine sitting static.
The pilot jet can become clogged very easy from either a piece of debris and or dried fuel residue, especially fuel with any ethanol.
In the pilot jet there are side holes [ diffusion tube holes ] that are larger and the main pilot orifice is in the very top. Usually in the .015 size. So very small. That has to be clear with no obstruction what so ever. If there is any it will lean [ lack of fuel ] the starting and idle circuits.
An air leak from the air box / filter to the cylinder mate surface also causes a lean [ extra air ] condition. Both conditions fit what you described.

Jim is, Jim Dirt. Long loyal CRF's participant as the few of us are still here from way back when CRF'sonly was a really popular site.
We bang on him because he is like a brother. You can't kill e'm so you have to love e'm.

[Andy Salmonsen]

Oh my god I keep forgetting things to ask u guys.

When I was taking the carb off the first time a little plastic piece broke off which held a breather tube onto a brass fitting with two breather tube connecting spots. My dad and I fixed it with some apoxy and brass tubing at there is no air resistance but could that maybe be the problem?

[Andy Salmonsen]

Ok, I may have not tightened the clamps to the carb enough so I’ll check that.
Also I put a filter seal in the Air box to have a better seal behind the filter so maybe that is letting to much air bye through the filter.
I’m gonna take the carb off anyway and give a clean so I’ll find the problem one way or the other.
Thanks for the advice

[Back2-2]

Andy, the picture of the fitting that broke is nothing in relation to your condition of running lean or hot. That is one of the breather vent lines for crank case pressure to go to atmosphere. Not sure about the red lines color, that may have been replaced at one time ?
Yes, check your clamps and look very close for any signs of cracks or tears in any of the rubber boots. Also as you stated check that seal you put in the air box to be assured it has not rolled over or left any gaps that could cause an air leak. There are ways to check for air leaks with different sprays around the suspect areas but we can get to that after you have checked the pilot jet.

As for 2-strokes, Don't run them down as they have become incredibly reliable and insanely fast, responsive, light weight and impressive machines. I have both 4 strokes and 2 strokes and they are all great machines. Don't bang on any bikes - they all have their place.
That said, these modern 4 strokes are light years ahead of the "Old Days" that Jim and myself come from [ not sure about Ray but suspect he is in the same or close generation. Not many years back a 4 stroke was nothing but a heavy, under achiever that was never considered more than a fat trail bike. Modern engineering have brought them a long, long way.

[Andy Salmonsen]

Ok just wanted to double check on that.
I just out the red tubes on the carb to make it look cool and that’s when I noticed the broken part. Also I never meant to harp on two strokes was just trying to make a joke about how everyone says to buy a two smoker when something goes wrong in a four stroke.

P.S. I put my dads name for the account my name is Landon. Should have put mine sorry about that guys

[Back2-2]

Ok Landon it is. I just wanted you to know that the 2 strokers out there have a reason they have 2 strokes.

One thing - that red colored hose in the picture. I get it - you added red hosing to anywhere that you could add it for the appearance. That is a breather hose coming from the engine valve cover or the lower area of the cylinder / base area to that junction point correct? It is not a hose with any relation to fuel delivery?

[Aussiecrf230]

Well in that case welcome to the site Landon.
I got that the 2 stroke thing was just having fun.


Neil,
I am 2-3 years younger than Jim but we are all that same generation of bikes we grew up with and probably couldn't afford as kids.

[Andy Salmonsen]

Yeah just a simple breather tube.

I have the carb off the bike and am ready to do some cleaning but I don’t know how to find the pilot jet. The only thing it says is a pilot needle, main jet and leak jet

[Andy Salmonsen]

Oh my god I think I figured it out. I have what looks like an after market pilot screw that can be turned by hand. I remember when I was first taking the carb off I turned it on accident but really didn’t think much of it. Still gonna give carb a clean but how should I adjust the pilot screw?

[Andy Salmonsen]

It’s a risk fuel mixture screw