350 big bore blow out

[Snakeoil]

Ricky, I'm goint to reply within your post for convenience.

ok ,

1. the engine was running rich because these was gas in both exhausts. the screws were turned 3.5 times by the way on the other (richer side) the one that popped was 2.5 turns. those carbs were never tuned the same though, it just didnt work that way, not suure thats the normal thing or not though. i know the tunining standards though caled for .5 to 1.5 turns only (max) . probably has to do with the increased displacement. the jet were set in the middle (default) .

The idle mixture screw controls air, not fuel. So when you open it up, you make it leaner.

Fuel in the exhaust is a complete mystery to me. With the bike running, you had raw gas in the exhaust?!! Hard to believe bike even ran. I would have expected that fuel to have eventually ignited resulting in one mutha of a backfire.

An overly lean mixture can cause an engine to backfire on decel. Too lean to fire in the comb chamber and pumps air/fuel mix into mufflers and when the mixture is right or the cylinder fires, BANG it pops out the exhaust. Very common in FI bike with low end mixture set too lean.

2. ok so yes, the engine must have been over heating. the run i did just before this one, the first for top speed, the engine started to smoke alot after the run (burning oil) . for future referemce, is this an indication of overheating?

Might have burned oil because there was poor ring sealing at first or you had an overabundance of oil in the engine and ports from the rebuild. But if you used a synthetic oil it could very well be that the rings would not seat. I've seen this before.

3. plugs i was running are NGK D8HA

4. timing, i will redo this but does bad timing have any sound indicators? i had a pro do the timing for me so i figured that was the least of the problems.

Getting paid to do work does not mean you are good at doing work. Horror stories abound for shops ruining well running bikes.

5. is there any way i can inspect for pinging now with the can open. should there be marks? because the bike would make a pinging type sound around the cam but i heard that was normal and not pinging by the mechanic. could tha have contributed cause?

I can see evidence in your photos. Top of the piston looks like somebody went at it with an ice pick. That is a textbook example of the effects of pinging.

You won't hear pinging at idle. It occurs under load. Mechanical lifters will rattle when the bike runs and mechanical noises are normal. But pinging is a very high pitched pink or ping sound that does not necessarily have a regular cadence to it like valve clatter. Best analogy for the timing of the pings is like crumpling up a piece of paper.

Excessive valve lash did not contribute to this failure.

6. about the molten aluminum. i have cleaned it out of the globe, it looks like some is in the exhaust port (more than the other side) ill assume because of the vacuum effect of the engine. does that need to be cleaned out? (looks like some on the valve stem) also i would hate to rebuild more than the top end. i have a magnetic plug on the bike. should that be good enough. (cleaning in frequent intervals)

Holy crap. Aluminum is not magnetic. If you do not know that, perhaps you should not be digging into this bike. Don't mean to offend, but this is pretty basic knowledge. I'm hoping you just had a brain phardt.


7. what oil filter should i clean, the one at the pump? or the one on the side. that one is a pain the ass to take apart by the way. any suggestions on how to open that one would be appreciated, but first is it necessary.?

If you want to be sure, follow Gman's advice and strip the engine. Next best bet is pull the oil pump and make sure it is clean. You could even dump a gallon of kerosene or similar thru the bottom end with the pump out, filter it to remove the swarf, and run it thru again. Do this until no more swarf shows up in your filter.
By all means clean the spinning filter. I'm amazed that you are asking that question.

btw, this hurts, i had about 500 miles on this rebuilt engine.

8 . one more, sorry,.. i had put in a new clutch basket. after about 400 miles, if you tried to feather into second gear the bike would not catch it right off, but kind off neutral out then suddenly pop into 2nd real brash seems like something would eventually break; the only way to get it in confidently was to pop it in a higher than mid rpms. any explanations for this? this may lead to taking the whole dam thing apart.

Sorry, but I don't understand your description or what you are asking. Not sure how you "feather" a tranny into gear. Shifting should be firm and positive, not slow and wimpy.

i put too much work into this bike for this, heres what she looked like before the black friday. also what i originaally bought her as (crazy)

Please don't take offense at my comments. If I think somebody might be better off not touching something because of inexperience, I just say it. It's your bike so you have the final call, of course. But if you just bought a bunch of parts and put them together without understand things like piston to cylinder clearance, ring end gap, carburetion set up, etc.. then I don't think you should be fixing this yourself unless you plan to do a lot of studying and learning before you begin.

regards,
Rob

[bonjour]

Pinging indeed indicates a wrong ignition timing !

Sparkplug type seems oke, but a 9 was probably a better choice if you want to drive it hard all the time, but that's not really the problem here.

Why would you run the bike when it's obviously not tuned good enough ? Running to rich also can do damage.
Lot's of gas mixing with the oil for instance, that also does not help to cool the bike !
Oil gets to thin, loses it's lubricating function, and then heat and damage will set in..

Lot's of mistake's where made here, the main cause is (what I think) a wrong ignition timing, way to much advanced....

These are really serious damage's and normally don't happen without some serious mistakes, I would say it's a real performance to make this happen !

But, mistakes happen so you can learn from it.
Next time try to be more precise, go in every detail of the engine, read and learn everything about it.
Because, if you need someone (a pro? come on, obviously he is not) to adjust the ignition timing, maybe you should ask yourself if you fully understand your engine.
As long as you don't, it's not very wise to demand all the power out of the engine.

I don't want to offend you, and wish you the best of luck, but this is just how I see it.

Please learn from your experiences so this won't happen again !

[rickytile]

about the tranny , what i meant by feather thing is that i would have to accelerate and be over 6k rpms while shifting between 1st and second for the tranny to make a solid engagement.

[Snakeoil]

about the tranny , what i meant by feather thing is that i would have to accelerate and be over 6k rpms while shifting between 1st and second for the tranny to make a solid engagement.

I'm at a loss. Maybe you clutch is not releasing or dragging and the high revs put enough force from the motor decel when you release the clutch to make it release enough to shift.

But it sounds more to me like it does not want to come out of first, more than it won't go into second. I wonder if sombody undercut the dogs for more positive engagement and this is hanging them up. Or, maybe you have something wrong on the spline that is causing the gear to bind, drag, call it what you want.

Maybe you have even more reason now to split the cases. Cleanliness and shiftiness.

regards,
Rob

[conbs]

Ricky, G-man, Snakeoil and Bon Jour have given you some very good advice in that you need to tear the engine completely down.

1. You apparently have transmission issue(s) that needs to be dealt with.
2. You will want to inspect your oil pump to see if that molten aluminum got into it and ruined it. Did you look at it when the engine was being built the first time? Was it ruined before you started having the last problems and not providing sufficient lubrication, which caused a chain reaction of friction, heat and piston failure.
3. You will need to painstakingly clean every part to make sure all that melted aluminum is removed and to determine if it ruined any other parts.
4. What about that timing? Is there an issue in your advance mechanism?
5. That is a mighty big hole in that piston which means it got really, really hot. There are fundamental issues that you need to resolve in putting the engine back together. That level of heat would cause a lot of expansion of the pistons. How scuffed are they? Was the smoke from broken rings?
6. Some of your questions are fairly basic as has been pointed out. Still, you could probably put the engine together again, but if I were you I would take advantage of every bit of help you can get from the experts on this site. I would take it slow and make sure you are sure as you complete each step. Post lots of pictures and ask lots of questions. A big bore kit and issues that go with it are not covered in the Honda shop manual.

You have a great looking bike. There is no reason it shouldn't run as nice as it looks. Best wishes on your project.

[rickytile]

Guys I wanted to simply replace the pistons or piston because everything else looks pretty good. so please help my with a couple of questions.


1. the pistons look like the oem ones. on the top of the piston, japan is written (punched in). it also says 3.00 on the top. on the side it says cb77.
i measured the diameter and its 62mm. (i measured 63mm for the cylinder by the way, is that the correct spacing? )

does anyone know where i could get these?

thanks much appreciated!!

[jensey]

Hi,

If my oil warning bulb flashes on while riding, I simply replace it with a broken one, that cures the problem.

Jensen