Break In Port timing suggestions?

DirtyBum

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Hi this is my first post!

SO I am fairly new to porting, I built a piston port 80cc which blew up (spun the bearing which in turn destroyed my piston and cylinder). I bought the cheapest cylinder, new piston, bearings, rings, slant head, reed valve, jets and a new sparkplug from Amazon and I am cracking my case today to clean out the residual bearings and such... I'll be balancing my crankshaft and planning down the mating surface while I'm at it. Parts won't be in until tomorrow and I'd like to port my engine for optimal performance at low rpms/climbing hills and was hoping someone could just give me some decent ballpark port durations for running a reed valved engine uphill, I've got a lot to do and I'm honestly just not trying to research and understand why exactly those port durations do what they do. I will be windowing the piston and I'm open to putting a trench/boost port in but I want to do this in under 6 hours as I am damn tired of working on the engine.

I'm going to be taking this baby on a road trip through the Appalachians (about 900 miles) in a week or two so not trying to do anything extreme or wonky which will make it unreliable.

Please limit answers to port duration suggestions as I already know it's not the best idea to go on a road trip that soon, I'm cold and the bike has been pretty damn reliable until the bearing finally gave out (modded too hard, I know what I did wrong and I don't wanna talk about it 🤣) and I am heading for greener pastures.

If I don't get an answer soon I'll keep my durations and just do a little cleaning and up and widening of the ports, that got me 35 mph before and was great going uphill until the cataclysm.

Thank you!
 

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900 miles... hope you have alot of spare crap lol cuz that optimistic to say the least. 165 to 170 exh 115 to 125 trans you have a pic of a reed so no point in intake. Not sure I'd use a reed on a road trip bike. Hope that loctite 518 or dirko ht red on your intake. Those numbers are ovb lower for lower rpm higher for high. DONT EXCEED 70% BORE WIDTH on porta
I had to use some JB weld to fill in the mounting screw holes (which were oval shaped) so that they could seal, blue loctite on the screws and red RTV on each mating surface between gaskets. Sealed beautifully. Why wouldn't you run reed on a road trip?

I can suggest port figures, but knowing what I would be starting with would definitely be nicer. Do you want to run piston port, reed valve for windowed piston or a boost port? Max RPM?

My ultra generic recommendations, if low rpm power is what you desire then....
keep the blowdown to about 20 degrees, maybe 22 tops.
For Piston port, 120-125 degrees of duration on the intake port.
Transfers 120-122 degrees
Exhaust: 160 degrees, give or take.

These are numbers for an engine with a power peak around 6000-7000rpm

A critical component of port work isn't just numbers, but shape as well. Making sure the transfers open and close at the same time is critical, and the upper transfer roof is parallel to the top of the piston and pointing the flow path to the intake side as much as possible.

I'm running a reed valve, boost port and windowed piston. I'd like peak power to be in the lower rpm range as I'll be stopping at red lights going uphill, climbing mountains. Peak rpms probably like 2500-3500 (if I had to guess)? I need it to haul me and my bag up many mountains. It worked before with the piston port but was really hard to get going uphill from a dead stop.
 
I had to use some JB weld to fill in the mounting screw holes (which were oval shaped) so that they could seal, blue loctite on the screws and red RTV on each mating surface between gaskets. Sealed beautifully. Why wouldn't you run reed on a road trip?



I'm running a reed valve, boost port and windowed piston. I'd like peak power to be in the lower rpm range as I'll be stopping at red lights going uphill, climbing mountains. Peak rpms probably like 2500-3500 (if I had to guess)? I need it to haul me and my bag up many mountains. It worked before with the piston port but was really hard to get going uphill from a dead stop.
There alot to unpack here 1. Red RTV isn't gas resistant. Even grey isn't very good BUT if you hafta then use grey. To seal surfaces against 2 stroke mix loctite 518 or dirko ht red are advised (they seal chainsaw cases). 2. A road trip motor should be focused on. simplicity. Adding ports and reeds is adding failure points. If you have a faulty reed(which is likely for a g2) your mega f***ed in some cases. Your asking alot from a little motor. 3. You will need a spare almost everything. 4. Doing anything from a dead stop is not advised. I hope you have an escape plan.
 
I had to use some JB weld to fill in the mounting screw holes (which were oval shaped) so that they could seal, blue loctite on the screws and red RTV on each mating surface between gaskets. Sealed beautifully. Why wouldn't you run reed on a road trip?



I'm running a reed valve, boost port and windowed piston. I'd like peak power to be in the lower rpm range as I'll be stopping at red lights going uphill, climbing mountains. Peak rpms probably like 2500-3500 (if I had to guess)? I need it to haul me and my bag up many mountains. It worked before with the piston port but was really hard to get going uphill from a dead stop.
My overall point even for an expert that's asking alot from a motor. You MUST be prepared to change your tune with elevation. These little 2 stroke won't survive 30 miles with a MILD lean condition reconsider maybe to a 4 stroke. At the very least run a sleeved cyl
 
I had to use some JB weld to fill in the mounting screw holes (which were oval shaped) so that they could seal, blue loctite on the screws and red RTV on each mating surface between gaskets. Sealed beautifully. Why wouldn't you run reed on a road trip?



I'm running a reed valve, boost port and windowed piston. I'd like peak power to be in the lower rpm range as I'll be stopping at red lights going uphill, climbing mountains. Peak rpms probably like 2500-3500 (if I had to guess)? I need it to haul me and my bag up many mountains. It worked before with the piston port but was really hard to get going uphill from a dead stop.
Just for full transparency. I'm probably one of the best for these questions. Impulserocket has some different technical knowledge but ask anybody I'm known for taking each motor to they're limit. If I HAD to do this it would be on this. I actually built another one last night. It's a 49mm iron sleeve. Upgraded BULLETPROOF pk80 top end. I've travel over 75 miles on 1 day in 90°+ weather tru difficult terrain with a full load including a belt sander I had to buy 25 miles away. It ran perfectly. It's THE most dependable 2 stroke they're is. I'm not exaggerating when I say ask anyone here I've owned and test virtually ever motor with every option. Showed absolutely no mercy. If it needs to be 2 stroke do it on an iron sleeve 1. No chrome to wear away. 2. Even with a part failure high likelihood it stays running. There's just so much to say about this. Keep vigilant any sign of change in operation has to be caught immediately.
 

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You MUST be prepared to change your tune with elevation. These little 2 stroke won't survive 30 miles with a MILD lean condition reconsider maybe to a 4 stroke. At the very least run a sleeved cyl

OK...I TRIPLE DOG DARE YOU...lol...lol....Take it for a nice long ride up to the Mount Washington Observatory and Weather Station, North Conway...lol...lol.


View: https://www.youtube.com/watch?v=uIsgSQvsRj8
 
My suggestion for the RTV thing is to use Hylomar. It is fuel and oil resistant and semi-curing so it never fully hardens. I use it to seal threads on fuel and oil line fittings as added insurance, and even on engine plugs. A tad expensive, but a little goes a long way. One tube of the stuff lasts me a couple of years easily, and I use it on a regular basis.

I'm running a reed valve, boost port and windowed piston. I'd like peak power to be in the lower rpm range as I'll be stopping at red lights going uphill, climbing mountains. Peak rpms probably like 2500-3500 (if I had to guess)? I need it to haul me and my bag up many mountains. It worked before with the piston port but was really hard to get going uphill from a dead stop.
Then I would use a degree wheel, figure out what your current timing figures and port durations are, and report back so we can figure out a port map. Otherwise, attempting to plan anything is pointless.

Most of the numbers I gave were to provide a power peak around 6000-7000rpm, which should give a good lower and mid RPM torque curve.

The biggest suggestions I could give beyond port figures is to port match everything, smooth it all out, keep the intake and transfers rough (80 grit or double cut burr finish), set your squish gap to around .8mm, and do the math to calculate case volume and make attempts to fill the case to increase case pressure for more transfer "pop" pressure.

Balancing and truing the crank will also lead to better longevity and just a nicer ride all around.

Then, even after all of that work you are probably going to still need to pedal assist it from time to time. No small little engine like this is ever going to power a person up a steep grade without either having an insane gear reduction or some level of human assistance. Want more than that, better upgrade to a motorcycle.
 
That's exactly what happened, well I tried to drill out the wrist pin with a regular drill like a dummy, which softened it and caused it to wear my easily. Overheating the bearing even with extremely rich fuel condition (which I did on purpose to get a feel for tuning as carb tuning is new to me) dug a nice little trench in the wrist pin, on one side. I flipped the pin so the other side would wear and switched from 32:1 93 to 50:1 87. Got about 50 miles on 50:1 and this happened the next day.

Well first I lost one of those wrist pin retainer clips when the engine was new, made one out of a spring that didn't seat properly. That's where a majority of the scoring came from. Ran without a retainer clip until I made one which properly seated. This was all in the first 500 miles. I beat the crap out of this engine already so I was definitely pushing the limits on purpose to see what she could do. I didn't do a proper break in either, so I knew failure was coming just didn't think it would be this fast. I was practicing for my trip, mountain roads with about 300 lbs of load strapped on (my 175 + 125 luggage) 40-50 miles a day... and 87 at 50:1 synthetic was just so much better on the hills. I'm veryy impressed with
the endurance of the engine.

My previous cylinder had been ported to
Exhaust 170
Transfers 122
Blowdown 28
Intake 120

This worked pretty well for my purposes.

My package didn't come yet with the heads and new jets so I built a spacer by gluing aluminum sheet metal together until I didn't hit the spark plug with the low hole piston. I honed the cylinder and put some slightly oversized rings in it (QA sucks but it worked in my favor lol) she's running like new with the old jug!!! I am expecting the head to be in today and jets by Friday. I read that I need to increase jet size to work with a reed valve, is that true?I've got a bunch of different sizes coming so I'll be able to tune to get the old jug just right and the new one with reed valve as well.
 
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