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Sherco overheating exaust


cascao
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Have a 2015 300cc sherco. On my last ride noticed a hudge amount of smoke from exaust. And some rear fender melting. It was during a uphill trail at moderate engine load. Have done it many times before without issues. To me it is clear that there something wrong. Checked water level, water flow, fan working speed....ok. engine temperature and power nice. Start easy hot or cold.

When I back home checked rear exaust blocage, carburetor, gearbox oil amount, magneto key and everyting seems ok.

Than, checked timming with stroboscope. 5mm btdc just after idle and 7mm over ~3000rpm. This look too much to me! retarded the timming as far as possible but keep having same readding.

Can be too much advance causing this exaust overheating?  is I am missing something?

Havent "kick back" issues.

always had few pinging when too much throtlle at low rpm

There is a leakage in reed valve rubber gasket....

Edited by cascao
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It seems that you have the mechanical skills, why not fix the vacuum leak at the reed block?

You know it creates a lean mixture which makes 2strokes run very hot.  Also, do you want to risk unfiltered air getting directly into your motor? 

 

It sounds like your pipe is burning off excess oil during uphill pulls.  This is fairly common with trials bikes due to a lot of slow running.  Oil builds up then burns off during hot running.  Do you have a spark arrestor or other screen that might be clogged?  You also might need to clean out and repack your silencer.

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Changed cylinder base gasket and no more leak. 

Rear pipe oil has burned on first time this hapened. Now there is not much smoke beside regular 2t smoke.

No blocage at rear exaust.

I will start to look at some weired ignition fault. Since everyelse look ok to me, bike run greath and exaust keep overheating when ridding at moderate speeds

Pick up coil white/black 200 ohms. Blue/red 20 ohms. Anyone have hidria ignition specs and timming advance?

Thank everybody for the help untill now. Lets keep ideas comming.

 

Edited by cascao
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The bike sounds 99% perfect except the smoke, so why bother too much about it if its the only symptom?  Maybe you are under exaggerating these moderate hills. Most  trials bikes will smoke heavily after a blast about and gasgas's even melt the rear tail pipe after a prolonged hard spell!!!

What oil and what ratio are you running?

Edited by faussy
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Generally 2 stokes don't have super hot exhaust but on long uphill pulls they will definitely burn off the excess oil.  Here is a thought.  If you can find another rider with the same model, pick up one of the electronic non-contact thermometers, ride up a long hill and compare the temps of the two exhaust systems.  It might even work with a couple cheap oven thermometers, hose clamped to the muffler. 

One thing I like to have when solving problems is data. 

 

Glad to hear you fixed the vacuum leak.

Edited by thats_a_five
Added comment about vacuum leak
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After this initial uphill trail failture I had doing my tests in a regular unpaved road most flat. Bike took about 5kms (3miles) to be at the point where rear fender start to melt. (Cruising at moderate speeds and load).

The buddy bike whitch rode with me never get close to it.

The heavy smoke has gone since everything inside exaust burned on first time.

 

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On ‎8‎/‎19‎/‎2017 at 5:00 PM, cascao said:

After this initial uphill trail failture I had doing my tests in a regular unpaved road most flat. Bike took about 5kms (3miles) to be at the point where rear fender start to melt. (Cruising at moderate speeds and load).

The buddy bike whitch rode with me never get close to it.

The heavy smoke has gone since everything inside exaust burned on first time.

 

Is there insulation on your fender?

Obviously one may experience heavy smoking and an actual fire in the exhaust when they get too loaded with oil.  Also slow(retarded) ignition will put a lot of excess heat into the muffler due to incomplete combustion and excess hydrocarbon downstream.

A restricted exhaust will get hot as well.

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12 hours ago, copemech said:

Is there insulation on your fender?

Yes, there is.

As pick up coil is fixed, there some effect in rotating the coils inside magneto?

Didn't see any hall effect sensors in this ignition.

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14 hours ago, cascao said:

 

As pick up coil is fixed, there some effect in rotating the coils inside magneto?

Didn't see any hall effect sensors in this ignition.

Leo, I di not have a Hidria on my older bike to test, however it appears to me that the hall effect sensors would be in the FIXED pick up plate and not in the actual stator coils used for making the power. I agree that 7mm BTDC for a base timing sounds excessive, and yet it seems you have no other running symptoms or kickback.

If I am thinking correctly, moving the stator plate on this will not change the timing.

 

I would suggest contacting Chris at Splatshop via email to see if he can give you other info or ideas and possibly just throw a strobe on a bike for comparison. He may even be able to help with some parts to try if needed, as it seems you may not be lucky enough to have a lot of other Sherco's around you to swap parts.

Refer him to this thread if he is not already aware, as he is a busy guy it seems.

Keep us posted.

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21 hours ago, copemech said:

Leo, I di not have a Hidria on my older bike to test, however it appears to me that the hall effect sensors would be in the FIXED pick up plate and not in the actual stator coils used for making the power. I agree that 7mm BTDC for a base timing sounds excessive, and yet it seems you have no other running symptoms or kickback.

If I am thinking correctly, moving the stator plate on this will not change the timing.

 

I would suggest contacting Chris at Splatshop via email to see if he can give you other info or ideas and possibly just throw a strobe on a bike for comparison. He may even be able to help with some parts to try if needed, as it seems you may not be lucky enough to have a lot of other Sherco's around you to swap parts.

Refer him to this thread if he is not already aware, as he is a busy guy it seems.

Keep us posted.

Will do this next week. Thank you.

 

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  • 3 weeks later...

Updade:

Managed to broke a rib in a competition two weeks ago while ridding my other sherco. (It was a hard enduro event with a trials class.)

Back to Exhaust thing, rode the bike yesterday. Spend a gas tank in easyer trails and unpaved roads (since still have some pain). Bike run greath, can't put my gloved hand on exaust for more than 5 seconds but at least nothing melted. It's useable at least.

 

99971440_043.jpg

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