Magnetic Metal grains in oil on spark plugs, how bad is it?

[titan performance]

I thought I read somewhere that you were told to go up 3 sizes from stock on both jets, but I can't find that now?

Anyways....stick with your pilot at one size over stock, and increase your mains. You did say the motor was flooding, but reluctant with the throttle open.....which sounds like it was rich at closed/partial throttle, and too lean at full throttle.

Just to re-cap.....you are using 32mm Mikunis with 97.5 and 30 jet sizes as standard?

[titan performance]

Were these fresh bores with new pistons and rings when assembled? The excessive carbon is probably due to you putting extra oil in the fuel, which could well be why you fouled plugs too.

If the bores were freshly rebored, are you confident in the quality of the job that was done?

[Pete O'Dell]

I would suggest mains are going and its burning gearbox oil too, have a good look at the con rods as I did tell you what chris applebee does with the rods.

[Nicholas]

Hi guys, thanks for the help. So, yes I was told go up three to four sizes. My bike was stock with VM32 carbs and I replaced all the parts in the carb with NOS genuine Mikuni even got new needle jets and jet needles, all 188 series...think I bought the last 4 NOS parts!

Now stock, it's 97.5 main and 3.0 pilot. When I put the Jemco pipes I went to 107.5 (4 times larger) and put a 3.5 pilot and put the needle on position 3 (stock).

The barrels were left stock, I just honed them. The pistons too, I just cleaned them up, polished and chamfered the skirts too, to allow for oil to stay in the cylinder....read this in a two stroke tuning book.

I should point out that my home made oil lines, although looked great with PTFE, they let air into the lines so it wasn't a continuous stream of oil, I bought used set, one good and one bad. I reverted to my partially working one and did a quick ride, then a plug read, 'brown' great! Stupidly took the bike on the journey!

On my way to Dover (from London) it was all running fine, i was loving my new ride smoke and noise, people stopped to stare! hahah Throttle seemed good, it had a dull note and lagged a bit when I accelerated quickly, but it all seemed good overall and the top end too..(so could have been lean at te te, I was silly not to check)

The trouble started about 2 or so hours later. I took a break for 60mins and when I started it fowled the right plug (the cylinder with the dodgy oil line). I replaced the plug it started, but it had idle issues and acceleration seemed off, it was ticking fast..I cannot remember if it kept stalling, but when I turned it off it was a mission to start again. It seemed to get progressively worse as the bike warmed up and especially the following day. I think the top end started to rattle then too. When we got to Calais I was having more troble getting it started and needed to hold the throttle open to keep I from stalling when idle. (All these problems were new on day 2, my short test rides the two days before we're pretty good, I was then occupied making a gear changer so had no time to test ride)

On the way to Paris I had an airfilter come off the carb on the motorway which i think flooded the engine. Once I duct taped the filter back on it took me 20mins of kicking to bring it back! When I made it to paris i realised the jetting was too poor and decided to send it back to London where I had my extra jets! doh!

And now....
On Saturday, I;
Fitted another used oil line on the right, thankfully it's perfect!
Put the 3.25 pilot on it and tried to tweak the air and idle screws.

I felt like it was at a good point and I decided to try it, I think it felt better. Still had the dull note and lag at 3/8 to 1/2 throttle, but it seemed better, I figured I could lower the needle position to lean things up a bit...I kept the 107.5 main jet.

About 10mins later it started to act up...the right cylinder started to clog up and did some crazy backfire through the carb....and it wouldn't start...I finally got it going but the right crab was popping in a bad way...so I gave up and pushed it back. It was then I saw the metal grains in the oil on the plug. the metal was not large, like very small grains of sand...with that I called it a day and started seeking recourse on here!

I'm thinking that maybe, the 3.25 pilot may still be too rich, or i need to dump my fuel to remove the traces of two stroke and try again with fresh plugs and fuel. Ill get a set of 3.0 pilots and give then a shot too....I don't know about the main jet, will keep it at 107.5 for now.

The plan is clean out the barrels and head, put in the damaged pistons and get the pilots working then take it to a dyno and sort out the mid rage and top end jets.

Pete, do you think I should open the crank case and take a look? I guess there is no harm, just time...I'll do it if it makes sense.... You think the con rod bottom ends could be suffering?

[Nicholas]

I would suggest mains are going and its burning gearbox oil too, have a good look at the con rods as I did tell you what chris applebee does with the rods.

I did check the oil level and it seemed to have dropped a little. So you think I should open the crank case and have a look. Ok, anything not obvious I should be paying attention to?

Thanks for your help Pete

[Coyote]

Main jets are too large. You should only be about 2 over. With all that carbon build up, you were bound to be suffering from pre ignition. Carbon was building up fast and in my opinion that's why it got progressively worse the further you went. Then it got hard to start as the carbon build up throws off the ignition timing.
This all theory, but that's how it seems to add up to me. What kind of oil were you mixing with the fuel. That build up is the worst I've ever seen. Especially with low mileage.

[Nicholas]

Main jets are too large. You should only be about 2 over. With all that carbon build up, you were bound to be suffering from pre ignition. Carbon was building up fast and in my opinion that's why it got progressively worse the further you went. Then it got hard to start as the carbon build up throws off the ignition timing.
This all theory, but that's how it seems to add up to me. What kind of oil were you mixing with the fuel. That build up is the worst I've ever seen. Especially with low mileage.

Right, the main is too rich.... then what caused my cylinders to overheat? or you think the metal came from the crank?

I was assuming that perhaps my motorway riding caused it to run with the mains and they were too lean? Or would have I had small end damage?

What do you think it could have been? I'm undecided on my best course of action open the cank case and get it checked out....or put it back together with the cleaned up pistons...do the jets then run it for a month and then re bore and replace pistions and rings..... or is that madness? if i do the crank is there s cheap way i could do it by inspecting it myself? what do I look for?

So the carbon was really bad huh? Was The state of the engine in a bad way for even the smaller pilot jets? i think i was still having trouble with the 3.25, but there was left over two stroke oil in the fuel tank.

The two stroke oil i use is Castrol two stroke racing (the red stuff), thought this was good, right?

[tz375]

Do NOT polish piston skirts that just increases clearance and changes the shape - and not in a good way. I would also stop that chamfer trick and just build a clean correct motor.

On the highway a bike usually is running on less than 1/2 throttle, so the main jet is not really the main event. It's all about the needle jet and needle at that sort of setting.

The carbon build up is excessive but that's probably too much oil rather than too much fuel. A rich mixture typically keeps pistons crowns clean, but Pete O'Dell has seen more of them than the rest of us and can probably offer the best diagnosis. Those bores are pretty scored and would benefit from a rebore IMHO.

There's no sign in your pictures of pre-ignition or other distress, but were they before the Paris trip and if so do you have pics of the plugs and pistons after the trip was aborted?

[Coyote]

I don't know how to answer your questions as I don't own and never owned a 500. I was just trying to analyze your situation. If I were you, I think I would a complete tear down NOW as it still is not determined where the metal flakes came from. I think patching it up to tune your carbs is a waste of time. Your rings wont seat right with all that scoring in the cylinders. Tuning your carbs to a worn out top end will not help you at all in the long run. I would order pistons and rings right now and then have it bored to the pistons you receive. It's important that whoever bores it has the pistons in hand because no two are identical. They should be match bored and marked L/R. Clearance should be .0018 to .002.
I doubt this will help you as I am speaking of a GT550 with pods and chambers. I wound up a 3 over on the pilot jets and 2 over on the mains.
Good luck and keep us posted!

[Nicholas]

Okay, I'll do it the right way, I cannot start taking shortcuts after so much time and effort, I messed up and need to correct it.

Thanks for the advice.

So I need new rings and pistons and a quality machinist who will match the pistons to the cylinders. Should I replace the small ends and gudgeon pins? They were new parts.

I'll open the crank and take a look, I just hope it's all okay down there...it cost me a lot to rebuild the crank! If its not I suppose I can go back?

Perhaps it would be wise of me to get some professional help with this part, I'd rather learn from someone rather than my mistakes and it's getting expensive!

Maybe Pete O'Dell has some time to help me out...

[tz375]

I'd contact Pete and see what he can do for you. It's probably his busy season, but he may be able to fit in some of your work that others are less capable of taking care of.

[Nicholas]

I'd contact Pete and see what he can do for you. It's probably his busy season, but he may be able to fit in some of your work that others are less capable of taking care of.

I think it would be good if he could check out my crank too! Fingers crossed!

Oh to answer your question:
The plugs before France were good...then when one fowled, it just looked all oily and I don't think the top end was making noise then...it happened the following day...the barrels and pistons before we're in good shape.
The polishing and chamfering came from that two stroke performance tuning by Graeme bell...so I thought it was good..the idea was that a sharp skirt would pull the oil from the sides of the cylinders. I think I did it about .5mm so it shouldn't have opened ports?

I can say that the engine was rattling, so if the little ends we're ok, do you think the next culprit would be the crank? I'd say that's logical right? I spoke with the guy at Gibson and he said that it could be the seals in the crank and when the engine heats up it gets worse and compression is lost so it won't start...but I'm not sure about that because it sounded flooded when it wouldn't start...but I'm certainly no expert!

[tz375]

Plugs don't often foul (let alone turn into chickens ) unless the ignition is weak or there is way too much oil or fuel and it usually takes a lot of fuel.

The only way to know for sure is to measure compression and leak down and piston clearances. Just looking at the photos of the pistons (before) suggests excessive clearance but tat can't be measured from a photo. You can check little end free play and big end free play with a dial gauge and a little ingenuity and if it "looks" loose, have Pete strip and inspect the crank. He's done more of those than I have had hot dinners - not literally but you know what I'm saying.

Piston to bore clearance you can check with a feeler gauge to get a good idea if it's close to spec or miles off.

I'd start by posting AFTER pics of pistons and heads and then put teh top back on and measure compressions and leak down. It's always useful to start with hard data.

[Nicholas]

Plugs don't often foul (let alone turn into chickens )

Ha ha ha ha

[GT750Battleship]

To save all the advice on this one,just take the motor to someone "who knows" get it done properly,build Carbruetors to standard & enjoy the motorcycle,these old girls were made to be reliable & strong,never add extra oil to the fuel,creates more problems,always trust the pump!!!
Regards.
GT750Battleship.