Need some help with my first bike.

[Looby]

hello this is my first visit to this site and idk if im in the right spot or not but i have a major problem with my bike i bought a couple of weeks ago.

bike is:
1979 Honda CM400T

my problems:
1) basically the thing refuses to rev. it hits 4,500 rpm and just stops. i can rev it to 6-7 if im not in gear but it really doesnt like it.
2) it also has something wrong with the charging system its only putting out 12.5v instead of 14v...
3) doesnt want to stay running. i can start it and it will run ok then the rpms will slowly drop till it dies.
4) it did smoke like a chimney after about 10mins of riding but it has since stopped that but figured id throw that in.


guys i really need help i bought this bike and have yet to ride more than 10 mins and its killing me. any help you guys can provide.


thanks
Looby

[rexmitchell]

First guess you have carb issues, probly need to be cleaned good along with the fuel lines. Stator may also be bad if you are having charging issues.

[Dodsfall]

The carb cleaning is a good suggestion. Make sure your battery contacts are clean and snug. That's the problem about 75% of the time. If nothing is wrong there, trace back to the regulator and test that. A close inspection of the wiring for shorted wires, conductivity or corrosion may be needed. The last resort is to check for the proper voltage coming off the stator.

[Mustard97]

also check the gas tank for rust, and put an inline fuel filter for extra protection, if you do have rust vinegar works wonders, it cleaned up my tank on the 77 xl100 to almost like new condition after soaking for 7 hours

[Looby]

contacts are good (as far as i can tell). the acid was way down so i added and am charging now. the tank is clean and there is a clean inline filter installed. i actually took it out on the road today and it really didnt rev and the second i got off the gas it would die and it takes FOREVER to get it started again.

then as i was pulling in my driveway the engine started making more noise then usual and it died and refuses to restart. the engine spins fine so i dont think i broke anything but figured id add my most recent experience to aid in diagnosis.

for cleaning the carbs any particular way i should clean them? do i need anything (gaskets, etc) to put them back together? i dont want to get them apart then have to order a bunch of parts that could take a week + to get here.

[Mustard97]

timing off maybe? is your choke working?

[BikeCycleMan]

The carb float adjustment can also give you symptoms similar to those. Adjust them right when you clean the carbs. The best float adjustment is done with the carbs on the bike. With one float bowl off open the fuel and then raise the float to see if it cuts off the fuel at the right position.

[DoubleClutch]

You can also take a clear hose and put in on the fuel bowl drain nipple and hold it along side the carb bowl and open the drain screw and the fuel will stop in the hose where the fuel level is in the bowl.

[BikeCycleMan]

Originally Posted by Mustard97

timing off maybe? is your choke working?

Yes, make sure your choke is turning off.

[Looby]

choke only operates the left carb but it fully disengages and will run fine with 0 choke for 10 mins then after the engine dies i have to run half choke to get the engine to continue to run

[Mustard97]

if i'm thinking correctly, you may not be getting enough fuel after 10 min.

[67fire]

As Dods said, clean ALL of your ground wire ends and contact areas.
Throw a can of Seafoam into the fuel tank and report back after those "cures."

Eric

[Looby]

well i have already done the seafoam thing in the tank and straight in the carbs. and i will clean the contacts tomorrow night.

[Looby]

alright i took the carbs apart and they were almost immaculately clean... the one thing i did find wrong was the air cut off valve diaphragms were torn so i replaced them along with float needles.

my previous problems
1)still will not rev.
2)(FIXED)charging system is OK now
3)will not stay running
4)(FIXED)no more smoking

i played with the mixture screws and they dont do a **** thing. all the way in or all the way out makes no difference in how it runs. ideas? i really hate this im starting to think i made a bad purchase... idk just frustrated

[67fire]

Are the slides set too low for the jets to work? I.E.: Closed with no gap?

Have you physically seen the screw tips protrude into the bore?

Eric

[Looby]

uhh... (deer in headlights)

slides set too low? i know the slides move freely and the go up as the rpms increase

i cannot physically see the screws no but thats cause i have the carbs on the bike. i have tightened down till they stop and loosened them till they almost fall out and it seems to make no real difference in how it runs.

i found a good how-to on carb float height adjustment and ill try that. i ordered new float needles and when i replaced the old ones the floats seem to sit a LOT lower in the bowls so im REALLY hoping thats the problem...

also forgot to mention that it is backfiring through the carbs. i was told this could be a lean condition and that it could be incorrect timing. i also was told that this bike does not have adjustable timing. that if the timing is off it is either the alternator or cdi box. well im off to tinker...

[tylernt]

Originally Posted by Looby

i have tightened down till they stop and loosened them till they almost fall out and it seems to make no real difference in how it runs.

This tells me you have one of two problems (or, I suppose, both). You either have a vacuum leak, or, your pilot jet circuit is partially clogged. I know you took the carbs apart and they "looked" clean but trust me, you cannot tell anything by looking! The pilot circuit is very long and narrow and you cannot see inside it even with a screwdriver because there is usually one or more turns in it. Take them apart again, remove the idle mixture screws, and spray carb cleaner in the pilot circuit several times making sure a stream of cleaner comes out the other end.

How about the rubber things holding your carbs onto the engine? Any cracks? They have good gaskets? How about your throttle shaft seals?

[67fire]

What Tylert is refering to are the intake manifolds and the, prone to drying and leaking, O-rings to the cylinder head.
Part #'s 7 & 11 here:




Vacuum leaks at the O-rings are the most common.


Eric

[Looby]

well.... ... i am happy to say adjusting the carb floats made the bike run like a dream. i was able to rev to 8-9k without much trouble and it seemed to idle better with only the occasional hiccup through the right carb... pulled the plugs and i think i set the right carb a little lean but it was running great

that said i went for a ride up and down the street and then 2 mins later as i pulled back in my driveway and the motor stopped..... and when i say stopped i mean froze solid. the starter would not turn it the kick start would not turn it... i thought i had melted a piston or something but i ended up pulling off the clutch cover and come to find the balancer chain hanging limply inside the engine... i dont think it broke but i cant tell what happened. i do hear metal parts rolling around in there though...

my question how do i crack the case. ive got the engine out and all the bolts loose but i didnt take the stator off since i dont have a puller. the bottom of the case is free and would come right off but the part near the stator is still together. is there a bolt under the stator rotor that would be keeping it together? like i said the entire thing is separated except the piece right behind the stator.

also what is a drift tool? the manual said to use one to take off the clutch nut...?

[Looby]

well swift update... cracked the case and found many MANY metal bits floating about so im not happy. the rear balancer gear esploded... explosively exploded... i have found new parts on ebay but the main bearing cap assembly looks heavily worn and mucked up so im hoping to get one off ebay as well.

anything else i should do while engine is open or bike is apart? im currently painting and fixing the holes in the horribly rusted exhaust. im just wondering what else i might need to do.

[BikeCycleMan]

Wow! That's a real bummer for you right after you got the bike running right.
Believe me a lot of us here feel for you. Don't give up - you're learning a lot about that engine though it would be nice to be riding.

[EmperorGrahf]

I don't know, I'm pretty new to working on bikes, I would say check everything for wear while you have it torn down. pistons, rings... all of it

[Looby]

yeah this is my first time working on a bike. i have no problems tearing a car to little base components but this is my first time on a motorcycle. Looking through the engine everything seems ok... i wasn't able to do a real compression test with the engine warm yet but i couldn't afford rings so i guess ill just put it back together after a cleaning and hope for the best. hoping to get parts next week and be on the road the week after.

one more thing im wondering about is i see places like jcwhitney have internal baffles for pipes. they sell 2 different sizes but im not exactly sure how they go in the exhaust. the previous owner gutted the mufflers and they are kinda loud. i work in the early morning and i would like to ride to work but starting up a loud bike at 5:30am would get me killed by my neighbors. basically im looking for yalls opinion on either a baffle or some kind of new mufflers that isnt gonna cost me through the nose.

[Looby]

alright ****... i replaced all the parts that were damaged and cleaned the **** out of everything. i put it all back together and nothing. i cant even hand crank the engine around...?... i can only think of two things. 1st i really had no idea how tight to make the balancer chain so i made it pretty tight but i cant see it keeping the engine from turning and it turned fine till i put the engine in the bike. other than that i realize i forgot to put the recoil spring back on the kickstarter but i cant see that keeping the engine from turning either. if ANYBODY has an idea... i need some help i know i just keep running into problems but id really like to finally get this thing running.

[67fire]

Did you take any pictures while you had the engine apart that you could share with us?
More eyes might see the problem clearly.
Does it have a cam chain adjuster? It it automatic?
Did you try to adjust it?

Eric

[Looby]

no stupidly i didnt take pictures. i meant to but was all greasy and didnt want to get my camera...

no i didnt touch the cam chain at all during this process i was able to take the bottom of the case off without having to mess with the top end.

[Looby]

kk so i figured out my motor no turn problem thing. i didnt have the stator on all the way and it was binding. but NOW im back to the problem i thought i had fixed... i cant rev over 5k... it just will not do it. and it backfires through the carbs (mostly right side) and after i rev it it dies... it only seems to want to do this after its warm and been running for a few minutes. i am definitely happy i have gotten the thing running again but now im sitting looking at my bike like wtf...

[tylernt]

I know you took the carbs apart and they "looked" clean but trust me, you cannot tell anything by looking! The pilot circuit is very long and narrow and you cannot see inside it even with a screwdriver because there is usually one or more turns in it. Take them apart again, remove the idle mixture screws, and spray carb cleaner in the pilot circuit several times making sure a stream of cleaner comes out the other end.

How about the rubber things holding your carbs onto the engine? Any cracks? They have good gaskets? How about your throttle shaft seals?

[Looby]

i took the carbs apart and i did blow cleaner through all the orifices and they all came out fine. the rubber boots are great no cracks and i have them secured well to the engine.

[Looby]

uhh first is there no edit on this forum?

second i have done some reading around the internet and i read a similar problem with another bike and it turned out to be the cdi box as the box was not advancing the timing with the rpm changes. idk im gonna do a little testing tomorrow but we will see

[Looby]

k i rode the bike about 5 miles today. it still would not rev over 5k but i was able to struggle through the gears to get to 55mph. as i was on the final leg of my journey home all of a sudden the engine goes BANG BANG BANG (very mechanically) and boom boom boom came out of the carbs and the engine died. i coasted onto a sidewalk and the engine was frozen?!!!! wtf?

anybody wanna buy a bike? ill let it go for cheap

[tylernt]

Ouch! I didn't think you were going to try to ride it before figuring out the problem!!

So, back to the original problem of backfiring and not going above 5.5Krpm. If it's a vacuum leak, you were running lean. Lean means hot. Hot means one or more exhaust valves probably failed catastrophically.

If you're sure there was no vacuum leak at the carb or intake, your valves may have had zero tappet clearance so your valves were never quite closing all the way (which can burn an exhaust valve whether you're running lean or not).

[67fire]

No complete engines for sale today but,
maybe some of the parts will help:

http://motors.shop.ebay.com/i.html?_...=&_trksid=m270

Perhaps a CB500 engine will fit?

Eric

[Looby]

yeah i think it was valve. idk i cant figure why though i didnt have any popping or backfires it just didnt want to rev. i just figured it was the cdi box not advancing the timing but it ran great under 4k and since i was able to shift gears and leave it under 4 i figured it would be ok. i did take the plugs out and there are valve pieces in the cylinder. i have learned a lot in the short time of having this bike and will now just look for something bigger.

anyway im not spending any more money on this bike. i will be posting it to craiglist tonight and hopefully i will not lose too much money on it.

i appreciate all the help you guys provided and im sure ill be back when i get another bike.