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Post by headcoats on Jul 8, 2020 21:31:05 GMT 1
What clip position did you settle on with the N68A needles then ?
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Post by Tobyjugs on Jul 8, 2020 21:44:32 GMT 1
On the road i used the middle position. I have moved them up or down for the other uses, it just depended on they day and how the plug looked or the riding situation.
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Post by flames on Jul 8, 2020 22:16:21 GMT 1
Thanks mate. I am sure I have read this before. Forgot all about it, but enjoyed reading for a 2 Nd time. Very interesting |
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Post by tdrpete on Jul 16, 2020 21:27:48 GMT 1
My missus likes an odd backlash she reckons about 5 degrees before top dead centre is the sweet spot. Not sure about the squish or needles depends on the riding position. Hope this helps.
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Post by Tobyjugs on Jul 16, 2020 22:51:29 GMT 1
My missus likes an odd backlash she reckons about 5 degrees before top dead centre is the sweet spot. Not sure about the squish or needles depends on the riding position. Hope this helps. What about fettling the port? |
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Post by tdrpete on Jul 17, 2020 19:17:14 GMT 1
Stans the man when it comes to fettling the port better ask him lol.
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Post by 4l04ever on Jul 18, 2020 0:57:06 GMT 1
Stans the man when it comes to fettling the port better ask him lol. He has had his old tool in many a virgin exhaust port...then just gently opens them up... |
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Post by tdrpete on Jul 21, 2020 15:41:42 GMT 1
Finishing off with a nice chamfered finished around the port edge...
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Post by Tobyjugs on Nov 2, 2020 0:55:06 GMT 1
Now all the checks are finished i thought i would document them for the people that might find it interesting. Crankshaft
| Flywheel | Gearwheel | | Crankshaft Runout fitted | 0.03 mm | 0.05 mm | Big end axial clearance new
| 0.80 mm | 0.75 mm | | Big end axial clearance adjusted | 0.45 mm | 0.50 mm |
The nominal size of the pistons are 1.50 mm oversize and the make is PROX
| Flywheel | Gearwheel | | Piston/Bore clearance | 0.05-6 mm | 0.05-6 mm
| | Top piston ring gap | 0.25 mm | 0.25 mm | | Bottom piston ring gap | 0.30 mm | 0.30 mm |
The base gaskets fitted to this engine are 0.60 mm thick
| Flywheel | Gearwheel | | Compression ratio (uncalc) | 12.5/1 | 12.5/1 | | Squish band height | 0.94 mm | 0.98 mm |
(open/close) Exhaust port 197 deg duration Inlet Boost 128 deg duration Transfer port 130 deg duration Back Lash
Primary drive gear wheel 92 primary driven gear wheel 62B Back Lash = 154 Average clearance between gear wheels = 0,08 mm Just a short up date to this engine it ended up making power between 65 and 70 PK. One of the pod filters split. These were replaced with another type filter which had even more surface area. I didn't rejet and the engine seized. The bike had done about 11000 miles and was was just starting to think how reliable it was. I have now opened the top of the engine up and inspected a few things. I think because the engine seized solid on one piston there was little damage done to the barrel. I scrapped all the aluminium off the barrel and put a 180 and 320 flex hone through the barrel and it came up very nice. However once both barrels were measured it was a different story. The top of the cylinders measured roughly +0.05mm from the nominal size. The middle of the cylinders measured roughly +0.10mm from the nominal size. The bottom of the cylinders were still good. I mesured the pistons at roughly -0.10mm undersize. I also measured the big end axial clearance which was also not so nice. On the primary side the axial clearance was 0.80mm and the flywheel side it was 1.00mm. I'm now thinking it was not so bad that it seized. It was time for an overhaul. I'm just wondering if it was the hard life it had or the quality of the 2T oil used? |
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Post by 4l04ever on Nov 2, 2020 9:34:23 GMT 1
These engines seem to keep running well even when quite worn. A small amount of power will be lost over time, but it will depend on budget and power requirements as to when it is rebore time. It is amazing seeing the insides of some engines which were running well before disassembly. I once saw a pic of a TDR250 piston which had been running but was cracked in half through the gudgeon pins and across the top.
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Post by midlifecrisisrd on Nov 2, 2020 9:49:46 GMT 1
I'd hope it was the hard life as all 2 stroke oil is better nowadays and doubt you were running it on Carlube oil
A bit of bore wear I'd expect but the crank/big end clearance is the thing that jumps out to me
Would be interesting if you measured a new rod and saw how much was crank spread and how much was rod wear
Suppose the other thing is the crank could have spread early and been running like that since
How much small end rod deflection are you getting?
Steve
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Post by Tobyjugs on Nov 2, 2020 11:08:58 GMT 1
I'd hope it was the hard life as all 2 stroke oil is better nowadays and doubt you were running it on Carlube oil A bit of bore wear I'd expect but the crank/big end clearance is the thing that jumps out to me Would be interesting if you measured a new rod and saw how much was crank spread and how much was rod wear Suppose the other thing is the crank could have spread early and been running like that since How much small end rod deflection are you getting? Steve I never measured that I will do it when I rebuild the engine. Not sure what to do with the crank on this one, if the big end bearings are still good I might just press it back together and weld it. This crank came from MBD if you look at the measurement above it was just inside the recommended tolerance on one pin and just outside on the flywheel side crankpin. After a chat with Martin I decided just to adjust the crank myself. I want to say Martin did offer a refund. Just explaining the crank history. The plan was to try and rescue the seized cylinder or rebore it then put it back in the bike. |
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Post by midlifecrisisrd on Nov 2, 2020 11:59:59 GMT 1
That's the thing with the non OE cranks. The manual specs are for the Gen item, there is no guarantee the pattern stuff is built to the same spec
The small end rod deflection is a good indication of big end wear
Think the service limit is 2mm and I've seen 30k mile cranks still just in spec
Steve
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Post by Tobyjugs on Nov 2, 2020 15:35:34 GMT 1
In the beginning the rev limit was set at 10500 later it was changed to soft at 11000 and full limiter at 11500.
My crank in the 400 engine has had a colourful life. First it was out of phase. I corrected that. Then it also started to part. This was pressed back together and welded. Touch wood it's still good.
I mostly ride the 400 so it is better treated and only on about 5000 miles maybe less.
When the engine in this subject is back together I will pull top end off the 400 for a look. This is the advantage of an O-ring cylinder head. Cheap to do inspections.
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Post by Tobyjugs on Sept 13, 2023 12:42:29 GMT 1
Bump for Karlok
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