85 replies to this topic

[HAM2]

Hello T.C. technicians,help, please.
Tested my bike out at a trial yesterday (1st trial since engine re-build ) and it started playing up.

I have yet to begin the post-mortem,I'm so pi55ed off I need to calm down and think logically....which is where you lot come in

I'll give you the symptoms first:-

Bike ran mighty fine for two laps (it was a very small lap/trial) then on a small hill-climb the engine developed a lean,hot,pink.
I looked around for any coolant stains or odours but there was nothing un-toward.

I let the bike idle for a few minutes and watched the fan cycle in and out a few times, everything seemed ok.

Carried on with the trial.

After a few more minutes the heat and smoke from the exhaust got so bad I had to stop the bike and get off,at this point I thought I could detect the smell of burning ATF.

I nursed it thro' the last 3 sections and went home with a million different prognoses in my head.

I'm trying to give as much info as possible here:-

Prior to this trial I've tested/played on the bike a dozen times after the engine re-build,trying to get as much heat into it as I can(many high speed blasts to clear the exhaust) and the bike never,never missed a beat .

My favourite theory at the minute is the mains seals,the ones I put in were black, the ones I took out were green (are they colour coded?have I put nitrile in and took viton out ?)Would that account for any rapid deterioration of the clutch-side main seal ?

I realize I need to 'delve' but I was hoping you lot could help me with a diagnosis first.

Any theories welcome,
Cheers.
Wayne

[Dan Williams]

Could be. Found these materials property charts for seal materials. Viton has much higher temp rating.

http://www.pspglobal...ture-seals.html
http://www.ahpseals....h/materials.php

[copemech]

You may have just gotton it hot enough to actually light off the oil residue in the exhaust.

Did it run ok after cooldown?

You could actually measure the drained gearbox oil fairly closely. But i doubt that is it if it runs ok cool. . .

[max1956bikes]

sounds like ignition timeing has retarded.i dont know the model well can timeing slip?

[HAM2]

All good ideas,thanks fellas (keep them coming).

I can't get any spanner-time till Sat at the earliest...so more theories please !

[copemech]

Aye, If he did slip a keyway on the flywheel, it may be a bit dodgey when cool, but ? I think he did not bring it to proper torque by spec. though, worth a look if nothing else!

Historically, nitrile seals have worked just fine in my recall, yet for reasons such as this, I tend not to stray. I do not like being the test pilot! I am way too lazy!

[HAM2]

Ok ,here's the latest...(coolant full!)...washed and dried bike and it made no difference ...idling fine...still getting hot,pinking,fan cycling..not smoking ,so I had a spare 10 mins and went for the easiest inspection..the timing.

Everything was ok.woodruff key intact and timing as set (slightly retarded from the factory mark)..so I put the timing back to the factory setting and hey presto the pinking disappeared.

BUT,the bike still seemed mad hot (I'm only riding it around the drive),I need to test it on a run out to see if the pinking returns .
I think I've only improved the symptoms but haven't got to the root cause yet !

Now there's 1 theory discarded so I have a few more to explore ..would anyone care to suggest the next logical step?

[copemech]

I'm wondering if your fuel is tinged, maybe got some of that E85 stuff!

[HAM2]

Dropped the coolant and checked the impeller,all good so...had a bit practice last night and now she's drinking heavily as well ......at this rate I might be doing the same

Edited by HAM2, 10 July 2008 - 09:22 AM.

[PeterB]

Hi HAM2,
Not a lot to go on really, did you re-build the motor?
Nitrile seals are ok in the crank case for a time, say 6 months or so then the heat causes problems and they begin to leak. Not so much on the oiled side. From the overheating issue, I'd say the motor is drawing in air somewhere, are the seals in the right way around?(Spring in towards the crancase). Even if they are nitrile, they would still seal initially, for a while. Usually hi temp viton is used in the crank cases, or teflon.
Are you sure the fan is giving a decent blast, not wimpy.
After a rebuild, it is not usual to blast the motor to clear the exhaust, best to take it a bit easy so as not to load the motor and parts can bed in together. What was the rebuild?
Did you fit the oil seals with gasket sealant around the outside?
This is not a good idea as the seal can work loose.
As a rule, I wouldn't use nitrile for crank case seals.
No air leaks in the carb inlet manifold, exhaust pipe leaking.
Can't think of much else.
Good luck, PeterB.

[HAM2]

PeterB,thanks for dropping a line.

Here's some history--Main bearings--

I put black seals in (no sealant,springs inboard) and I don't know what they're made of??Doh!

Bearings were bedded in for about 20 easy hours run-time before I tried out the moto-cross track to 'clear out' the exhaust.

Bike has been really good for about 30 hours run-time.

Blown out the carb',washed filter.

Idle is meaty and consistent but heat and now thirst is the problem??!!(I thought rich=cooler?? )..the fan seems to be whizzing away, directing a very hot blast of air onto my legs!


Bear with me fellas,keep the ideas coming,I don't mean my responses to be --done that ,done that ,done that....I'm losing the plot

Wayne

[Roberto]

Hi. if the bike is running that hot, something is definitively wrong. What does the plug look like?? Is it the right plug. If not, it may not be drawing off enough heat. Are you sure the gas is premix at the right ratio? Is there a coolant hose somewhere that is kinked? If you are adding coolant it must be loosing it some where or maybe the engine didnt filll with coolant after the rebuild for some reason. You got a lot of things to check out, timing will be very important as well.

[PeterB]

Hi HAM2,
Have a look to see if the throttle needle is all intact, with a clip in place and the cable support washer in, are the carb throttle body vents venting to atmosphere, not interconnected. If everything mechanicalis ok, then the problem may be the ign system, I have no experience with Leonelli so can't really help there. The system may have failed and provide a retarded ignition, check with a strobe and see if the system shows signs of advancing as the revs build up.
Can't think of much more.
Bye, PeterB.

[copemech]

It is soo difficult to diagnose these things, even when you are there.

If the crank seals were leaking, the choke should make it run better after warm I would think.

Then you get to the HEAT thing. A slow ignition timing can give too much heat in the exhaust, as there is too much unburned fuel downstream. But a noteable change in preformance should follow if that were the case and the stator has gone off, or the box!
The strobe check would be good. As I recall, they should fire somewhere around 20-25 degrees BTC and show some advance with revs. A noteable change from this, say at only 10 degree BTC would be a good indication of a problem there related to the ignition actually functioning on the slow side of what it is supposed to be doing.

Unfortunately I have no hard numbers to go by.

Peter, would those numbers fairly match what you are thinking?

[HAM2]

Cheers boys,
I think I'm going to have to leave this topic alone till I get some serious spanner time(bloody weddings,christenings,emigration,family do's..oh,and work getting in the way) as I really have got little to give you to go on .

Roberto,PeterB, I'm not losing coolant(nothing kinky ),the plug is blackish/rich, not wet ,not sooty,not glazed?
Timing is at the factory mark and bike is rapid/powerful.
Carb' vents are clear.

Copemech, you are right when you say these things are difficult to pin point even when you are standing there,my mate (petrol in his blood,bike nut and fully trained mechanic ) was scratching his head at this one.

I'm not wasting your time on this till I've opened her up....thank you so far...watch this space (I trying to wangle a donor bike to try some transplanting )