Issues after rebuild

[trial_07]

I finished rebuilding my engine (crank, bearings/seals, piston/rings, timing chain, valves are new from late past summer) 2 weeks ago, the bike took a while to start but would run fine afterwards. I get back home, this past week end, and figure I'll start the bike just to be sure everything's fine before the season kicks off. The bike doesn't want to start. Choke, no choke, hot start w/ or w/o choke, no throttle, 1/4 throttle, 1/2 throttle, full throttle; NOTHING! What kept me kicking is that it seemed like it wanted to start everytime. Now I'm really angry because I've spent the last 3 or 4 week ends working on that bike. I get the thing back on the stand in the garage and start working my way to the check the valves. Lighting is not very good and it's dark outside so I'll figure it'll have to wait till tomorrow (Saturday morning). So, left intake valve is tight (0.07 instead of 0.12), right intake is dead on spec. Both exhaust valves are tight (0.20 instead of 0.28). I find this very weird since everything was in spec when I rebuilt the engine. I have only warmed up the bike a few times since, is that normal for them to come out of spec like that after a rebuild? I re-shim to the correct specifications and mount everything back up. I figure the bike'll start after two kicks, but no! Hell, everything turns over fine, there is compression, there is spark, there is gas, and the valves are dead on spec because I just checked them. So I tie the bike behind the car to pull start the thing. I totally hate to resort to this kind of technique because I know it can be really bad. The bike does start after a while. Everything runs good, it is very easy to start afterwards (once hot). I'm finally able to ride the first time this year, I'm happy! Bike runs strong, starts very well. I get back home after lots of riding and wash everything up, and do the normal maintenance after a day of riding. The next morning (Sunday), I'm kinda nervous to see if it will start. I kick a few times in the garage, nothing. I figure it's too cold in there so I bring it outside in the sun. After a few minutes, I get back on it. It wants to start, but doesn't. I finally get it with no choke on, 1/4 throttle, bingo! Afterwards, once hot, it's a piece of cake. I rode all day long, bike still runs good.

There's something I got to tell you, the spark plug isn't new. :bang: It's one of the only two I own since I got the bike. Could this be the reason why it is so hard to start when cold? I've got no more skin on a part of my right foot which is wrapped in a bandage and giving me a bad limp today. I'm really tired of hurting myself trying to start the bike so I really hope I get this issue resolved quickly. When I get back home next week-end, I'm going to open it up again and check if the valves are still within specs after two days of riding. I'm ordering a new plug this week.

So, can anyone tell me what's going on? Is it only the spark plug? Is it normal for valves to have a workout after a rebuild?
Thank you very much for any input and sorry for the long and boring narration, your help is appreciated.

 

[_JOE_]

I ran into a similar issue a couple weeks ago. In the fall I replaced the piston and valve springs. After the first few hours I rechecked the torque on everything and checked the valve clearance. The intakes had tightend a couple thousandths. Not sure why, maybe someone else has an explanation. What unit of measure are you using for the clearance? My specs are something like .005" intake and .011" exhaust.

As far as the cold starting, that sounds like lean pilot circuit. Have you tried richening the fuel screw? When it's hot do you need the hot start?

 

[trial_07]

My units in my previous post are in mm. I have not tried richening the fuel screw or make any other carburetor adjustments since the bike ran great last year. When it is hot, I do need the hot start.

 

[_JOE_]

Back the fuel screw out a quarter turn.

 

[whenfoxforks-ruled]

rapid wear on the valve adjustment sounds like bad valves and or seats. Regardless of hours on the bike. Who rebuilt the head would be the person to talk to. I have seen similar issues before. It is not a good sign, and be very religious about checking them. Same deal, more than 4 shim sizes from stock, its time for another rebuild.

 

[trial_07]

It is the first time I have to re-shim since I installed those valves last year. I don't think they're done yet, but I will keep an eye on them.

As far as the spark plug, could that be part of the issue? I'm buying a new one this week and don't know which one: R0409B-8 or R0409B-9? Which one would suit me best?

Thanks for the advice Joe, I'll try turning the fuel screw 1/4 turn counter-clockwise.

 

[Rich Rohrich]

It is the first time I have to re-shim since I installed those valves last year.

Did you replace the valve springs when you replaced the valves?

Did you have the valve seats re-cut when you replaced the valves?

 

[trial_07]

Yes, the springs were replaced with the valves. No, the valve seats were not re-cut when I replaced the valves. Everything is Honda OEM.

 

[whenfoxforks-ruled]

You never read the part from Eric's memoirs about oem valves being out of round, new. And of course an old plug will have starting issues.

 

[trial_07]

The reason I'm convinced the problem isn't valve related is because it doesn't act like if it was. Normally, when the valves wear out and a re-shim comes necessary, the bike won't start with choke or no choke on, but will with the hot start when cold. If the valves would be the problem, wouldn't it be hard to start once warmed up also? I remember a day last year when I finished one heat and the bike wouldn't start for another heat. This time, it does start very well when hot. It really is the first time of the day that's giving me trouble. The thing I can't explain is why they have come out of spec after only starting and warming up the bike after the rebuild.
I can tell you I'm a bit nervous because I can't afford at this time paying 350$ for new valves and machined head. I will open it up again when I come back home and I truly hope things haven't budge in there.

And about that plug, does it really matter whether if it's an 8 or 9? I remember reading a thread with all the info on this matter, but I can't find it anymore.

I will invest in Eric's CRF handbook. Thanks to everyone for the input.

 

[Rich Rohrich]

Yes, the springs were replaced with the valves. No, the valve seats were not re-cut when I replaced the valves. Everything is Honda OEM.

Running new valves on old seats is a great way to hammer the new valves in short order. I don't think it's the cause of your current problem , but it will be a problem some where down the road.

I still can't imagine why you would go through all this and leave an old sparkplug in the engine.

When you troubleshoot any problem you look at what you know, and you always start with the basics. Fuel, spark,compression.

So a sharp mechanic would :

- put in a fresh plug
- clean the electrical connections going from the stator to the CDI box, verify there is a good solid ground, and make sure all the connectors seat properly.
- Clean and inspect the plug wire and the sparkplug boot while looking for cracks or other damage
- Clean the pilot jet to make sure it isn't clogged or partially blocked. This is an incredibly common source of problems when bikes sit for extended periods. Even a small amount of old fuel in the float bowl can cause deposits that can restrict the tiny pilot jet orifice.
- Verify the air jets in the mouth of the carb are clear of air filter oil and dirt. They get blocked easily.
- Carefully recheck the cam timing. Lots and lots and lots of mechanics far more experienced than you have inadvertently set the cam timing one tooth off. It happens far more often than you think.

Once you can eliminate the majority of problems that come from the basics, then start looking for demons.

The fact that it starts easily when hot but not cold would point to a fuel restriction (like the pilot jet). You need very little fuel to start a hot engine because there is always some liquid or partially evaporated fuel left behind in the intake tract. So even if the low speed circuit is restricted the bike will tend to start. When an engine is cold there is no old fuel left behind, and the fuel that does make it in is reluctant to vaporize, so you have to add more than would normally be required. Hence the use of the choke. If you take that fuel away it can be difficult (or impossible) to start.

 

[trial_07]

The spark plug was a stupid mistake from my part. I will inspect and clean everything you described. The cam timing is right on, I always triple check before closing everything up, but I still will verify when I check the valve clearances. Thanks Rich for your help!

In the future, is re-cutting the valve seats a job that should be left to very experienced mechanics? I have access to CNC millings and lathes and the help of a very experienced machinist. If I bring the service manual which describes all the angles and dimensions, could he successfully do that job for me?

 

[oldguy]

- Carefully recheck the cam timing. Lots and lots and lots of mechanics far more experienced than you have inadvertently set the cam timing one tooth off. It happens far more often than you think.

.

Yep even the very best in the business can sometimes do this. Eric Gorr supervised Spider doing a topend on his 450. When he fired it up it the first time it fired just fine but the next week (next time it was started) he kicked and kicked for 10 minutes, we then bump started it and had a 4 foot back fire out the pipe everytime he let off the throttle. Ran back to Gorr's shop where in 10 minutes he had the timing reset and bike running like a champ.
No way I blame Eric Gorr as he was watching over Spiders shoulder and Spider should have caught the marks but it was a great learning experience

 

[Rich Rohrich]

In the future, is re-cutting the valve seats a job that should be left to very experienced mechanics?

Yes.

I have access to CNC millings and lathes and the help of a very experienced machinist. If I bring the service manual which describes all the angles and dimensions, could he successfully do that job for me?

It takes specialized tools to do it properly, so don't count on it.

 

[trial_07]

I see. And for the plug, does 8 or 9 really matter? :)

 

[whenfoxforks-ruled]

http://www.dirtrider.net/forums3/showthread.php?t=92818, You get to read, read your plug that is. When you check and double check the timing, spin the motor a couple revolutions, the bikes with 2 cams get to be more finicky.

 

[Rich Rohrich]

I see. And for the plug, does 8 or 9 really matter? :)

From the standpoint of starting the first time with a new plug, it doesn't matter. Once the engine is running having the proper heat range plug is important.

 

[trial_07]

Is there a way for me to know which one would suit me best without having to ride the bike and inspect the plug afterwards? They're 25$ plugs, I'd hate having to buy two of them...

 

[Rich Rohrich]

Is there a way for me to know which one would suit me best ...

Use the stock plug Honda recommends. Surprisingly they actually know what they are talking about.

 

[trial_07]

I guess that would be the 8? The only difference between both plugs on the fiche is the 8 has 001 in "Required" field whereas the 9 has (1). So I figure the 8 would be the stock one, and 9 as an option. Am I right?

 

[Rich Rohrich]

I guess that would be the 8? The only difference between both plugs on the fiche is the 8 has 001 in "Required" field whereas the 9 has (1). So I figure the 8 would be the stock one, and 9 as an option. Am I right?

Correct. The 9 might be needed by someone running it flat out for extended periods like desert racers.

 

[trial_07]

Great! Thanks again for your help. I'll tell you guys how it works out this week-end.

 

[trial_07]

Hmm...did I say 25$ plugs? They're actually near 40$ with taxes :whoa:

 

[oldguy]

Hmm...did I say 25$ plugs? They're actually near 40$ with taxes :whoa:

almost half the price of that new exhaust system :coocoo:

 

[trial_07]

almost half the price of that new exhaust system :coocoo:

It's ridiculous! I phoned the local dealer this morning and he said they were 55$ plus taxes. I said "Thank you, have a nice day". I then phoned to the local dealer at my home city and he had a better price of 30 something dollars. MidWestActionCycle sells them for 16.99$, but if I want to get them before this week-end, I need UPS, and if I take UPS, I'll end up paying 30$ shipping for this part only. I love this sport :) .