The piston wear is due to stroke, rod length and angle not the pin position. The rod ratio is well known 'phenomena' and promotes a lot of discussion. (and even more misunderstanding) Rod ratio's are usually in the 1.6 to 1.9 : 1 range, depending on what the designer was aiming for and intended use. Longer rods put less skirt load on piston simply because there is less rod angle at 90 degrees after TDC. I'll let everyone into a little (well known') 'secret' relating to the intake port you showed. That will have bad flow but it may be deliberate to cause extra turbulence and mix fuel better? Air doesn't like to change direction. If you look up some old NACA research from 1940's, about seven degrees is maximum divergence even on a fully pressurised system. I'm kinda old, been doing two stroke (and four stroke) motorcycles since early 70's.when piston porting was the only thing around Saws look a lot cheaper to mess with when you can buy a new Chinese motor for less than $100. Squish clearance closes up pretty good due to ball and roller bearings 'everywhere' plus con-rod stretch, piston just clearing head at max rpm is OK but may destroy several engines before you find the minimum. I found a one degree difference between piston crown and head works real good with about 0.038" on motors I've built. I don't usually work on 40mm bore or smaller cylinders though, 54~56 mm is usual for a 125 MX bike
Ironhorse, if I get a Hyway cylinder kit for my 372xp , do I need to check any of the timing on the ports if it just stock. I'm just using it for firewood gathering and don't need it hopped up .😊appreciate your input .
Rule number one…. Harv is right and your wrong. Rule number 2. See rule number 1. Ive noticed that high compression saws tend to vibrate more. Have you experienced this? High compression is good and all but after so much your fighting the compression and going backwards arnt ya? Im no professional but i dont care for super high compression saws.
Yer right Kyle! Too much compression and the piston slowes down too much before tdc! And then it fires real hard accelerating the piston! This is where the vibration comes from!
Hello buddy, hope u r getting u some rest/sleep. But what is tht bhind u Mr. Harvey 🤷♂️ im building a little 355 roller motor right now for my lil 98 stepside s-10. I got a set of dome pistons for it, have a nice cam for it also, @50 its a 254/266 with .600 lift. Thts with 1.5 rockers. Anyway i hope and pray ur Dr can get u all fixed up so u can keep doing what u love to do. And thts building saws 🙏 GETRDONE Mr. Harvey 🤙
I have a question for you....I have an 048-042 and was wondering if the 038 heads are interchangeable? Parts for this seem to be slim and few and far between... And some of the hwy robbers on Ebay seem to think they have gold... so I am looking for possible interchangeable parts...
Ya got to keep up the maintenance, change oil adjust the valves, to keep it running properly, and valve overlap is very important, you would think that would hurt performance, but it is almost everything, 😆 what's that to your right shoulder, the Saw is that for 😆,. It's just like the wrong cam , good day✌️
So I've been watching your video along with a couple other guys that build two strokes and it seems all of you guys do smaller engines so my question is I have 139 cc I want to put on a mini bike what would be the best port job to do like should I raise the exhaust port or what would be beat any advice would be greatly appreciated
Folks can yap away till the cows come home about blowdown , machining,port shapes, widths , duration ,squish bands , pistons mods , dynos and any number of alterations to enhance the performance of a chainsaw. Imho the modded saw must 1) increase cutting speed, 2) get good mileage and 3) last near as long as a stocker for it to be worth a damn …. A 70cc “built” saw with a sharp chain should be able to pull 1in /sec or better using a 24” bar/chain thru a 21-22” log/round (HARDWOOD not pine or balsa) with larger cc saws maintaining this 1in/sec with longer bars / bigger diameter wood. This is where da rubber meets the road and what separates the wheat from the chaff ! IF the saw cannot pull this 1in/sec (or better) than hit the bricks 🧱 bub. All this 2-stroke theory was worked out 50 YEARS ago by men much smarter than either you or I - These gospel according to masterboob , must be machined / 12 deg of blowdown high compression wondersaws simply cannot pass the 1in / sec standard in REAL HARDWOOD ! They just CANNOT DO IT hee hee hee 😂
LMFFAO!!! When us crazy guy’s get older that whole fear of doing life in prison isn’t nearly as scary when you might only have a dozen or so of those left!!! 😂😂😂😂. Those older fella’s shouldn’t be messed around with because they don’t have as much to loose the older they get!!! 😂😂😂. I’m all about 154 and not more then 156… but I just can’t really do anything without see my port mapping and actually seeing the engine!!! I just love when you are feeling scrappy brother!!! LMFFAO!!! I’m an old redneck boy so a good scrap is always fun! 😂😂😂. You’ve helped a whole bunch of guy’s build them a really decent work saw and they didn’t have a lathe and they have a strong runner! And obviously if a guy has a lathe he’s going to be able to get a stronger engine if he’s doing it right! Just cutting the popup into the taller pistons is the huge benefit as well as trimming the base’s!!! Great video Harvey! Nothing but love for ya brother!!!
hi harvey.very good explaining.a have a question.what you think its better in intake polish and smooth or little bit rugged surface?have heard many teories about it.
Hello there Harvey and hello to the saw community I was just wondering if you know of a lighter riste pin that I could use in a Husqvarna 262xp if you could let me know that would be great and eny other recommendations thanks
I dont know what to say, re-affirming, learnin... this is getting really good now, working the individual parts to get numbers more so than machining and helping a little bit of everything, everything I've ever done to my saws per exact uncle harv teachings have and are amazing machines. Look good buddy good to see ya
Just discovered your channel, and I am impressed. I am out of action for a while due mishap and interested in building solid work saws. After watching your other videos, am curious what the recipe you would lean(pun) to for an aerial saw for steering softwood/hardwood tops. You have mentioned the scenario in your videos but as far as I can tell haven't discussed the super reliable but performance logging/topping (work saw) incl keeping vibration down
Watched this again, caught more the second time around. Thank you Harv. Looking forward to the next part and praying for your full recovery. You're the man Harv.
I’d be really interested to better understand how it all changes when you add reeds into the mix and how that affects blowdown or if at all. The way some pioneers p series are designed almost makes me think they’re made to shorten the blowdown
A reed valve motor allows for asymmetric intake timing but doesn't change much else. The intake can 'open' as soon as there is crankcase depression which would generally be a 'free port' without the reeds. Prior to reed valves, it was far more common to have a rotary (disc )valve opening directly into crankcase. It does make motor wider though. You still have piston controlling transfer timing and exhaust timing
Harvey I've got a question that nobody seems to be able to answer, maybe somebody can answer it here. I understand the oil gas mix, but how is that delivered to the rotating assembly? How does the bottom end receive its lube to the bearings? I've asked this question on a couple real popular saw channels and have gotten completely different answers. Anybody feel free to chime in?
@@williamwallace9620 are you suggesting that the cylinder and the crank case are hollow and connected in such a way that the mix has a way to reach the rotating assembly and then make its way back into the cylinder? You could be right, I've gotten so many different answers regarding this. thanks for your opinion.
@@williamwallace9620 you did a nice job explaining that,I'll buy it. I'm pretty engine savvy but have never torn a saw down to see how it all jives, thanks again for your time
I just finished modding my g372xp. I am outside of your specs. I didn't want to do any port work so this is what I did . I modded the exhaust per your instructions on one of you other videos witha 3 inch piece of 3/4 inch pipe. I unshrouded the bottom of the tansfers by cutting the flanges out of the way. I installed 3 base gaskets and a slab sided flat top 268 piston. I ended up with .025 squish, 160 degrees intake duration and 155 exhaust. I just finished it and made a couple of cuts. I am impressed with how the saw runs. Maybe not ideal but it is definitely stronger now with minimal effort. Maybe I will epoxy the bottom of the intake next. Bring it to 150 degrees.
Thank you so much for sharing your knowledge! I built a 359 modeled after what you shared on tin man's 372 build. OMG! That little saw is an absolute animal! It contends with many of my 72 Cc saws. I wish I could say I fully understand everything your saying. I don't, but the principle makes sense and I'm trying to apply it and learn as I go. Thanks again. Take care of yourself.
I have followed your information to the letter on my first 372 build and it’s truly unbelievable. The response and power in the cut is night and day over stock . My buddies that have seen heard and ran this saw know . Full faith in you Harvey your specs are perfect buddy , thank you for your guidance and information sharing. No machining needed to get impressive gains . 🇦🇺👍🏻🇦🇺✊🏻
Glad to see you getting back out to your shop , your channel is terrific. … Question, with the exception of carbon deposits in transfer ports , is there a way ( ie:piston reading) that one can tell if the transfers are to high ? I take your knowledge quite seriously & it HAS changed some of my techniques,again thanks IRON Horse
I’ve watched your videos from 3 years ago over and over. Ported my 372 this winter from what I’ve learned from your videos. Big bore gasket delete.Thanks Harvey saw runs great.
Hi Harvey, You methods of saw building have worked for me. I add one of my custom pipes and a sharp chain, and that equals reliable pure fun! Thanks for sharing your years of experience, that can't be replaced!
I’d like to see a longer rod and a gudgeon pin closer to the top of the post too. Same stroke but would be a much stronger combination. Though I don’t know how far you could take it. In the performance V8 world like in your last video, some pins are are so high, they have to make special plugs to support the rings. However, that could be pushing the envelope way too far for a saw
Hi Harvey ~ I ran into an older (3 year old) Ironhorse video in which you couldn't sleep until you compared the stock jug from a Dolkita 7900 to a bigger top end you had in your shop. We now have a brand spankin' EA7900P here, so I'd really like to learn whether or not that upgrade actually panned out for you? Did you make an additional video about that 7900? I've just liked and subscribed, so please keep up with the fine video work, sir.
If anything, we should be tapering everything opposite to flow direction. To build velocity. That also slows the velocity at which the flow comes back in for the exhaust or out for the intake. Could probably also do that on the transfers.
Awesome info as always thank you from NZ 🇳🇿 ! Any chance in future of getting a video on Porting a dolmar 9010 ? Seems like a great platform for building a torque monster with the large stroke ! Take it easy man !
Long intake duration and too high transfers(not enough blowdown)will use alot of fuel. Also if your upper transfers are poorly shaped you will have short circuiting happening. Long intake creates spitback and wastes fuel. Higher you go on transfers more you will short circuit fresh air fuel charge trough exhaust port and muffler instead of keeping it in the chamber and making power. There is a point when givin the saw more fuel does nothing and if you build work saws you want to have good fuel economy. I dont port for living but its just common sense.
Hey Ironhorse! I just ordered some parts for my Stihl 660. I ordered a 54mm pop up piston. Would you recommend a gasket delete as well? Would you have went with the big bore?? 🙏
Love your videos. So I have a 462 with intake and exhaust at 160 degrees..... I'd have to run a piston with lower skirt to get 154° and should I delete base gasket cause that's just gonna Increase the intake? Thanks
Thank you Harvey for your expertise in two cycle performance design. I don’t really understand it yet, but I very much appreciate the passion and hard work you put into explaining this to us. I like the whiteboard tutorial someday, as a picture is worth a thousand words. I do like listening to your words so maybe we can get both.
On my 372 with a 272 piston I used some of your knowledge I angled my upper transfers up above my popup piston and not to raise the transfer too much It helped. Today I did a experimental muffler mod and it really runs strong now. I agree too much machining can hurt performance like making the combustion chamber small and making the area for the explosion small so there is less area to push on the piston. Which means less power.
That platform likes good intake flow better than anything. It also helps to widen the bottom of the transfer ports. That's what has worked well for me.
@@jerseyjoshua4818 has nothing to do with me so I cld care less that's for anyone that has a issue to deal with. Buckin Billy is a no bullshit tell it like it is guy and watching him run a iron horse saw is all the proof I need as far as build quality. Don't want anything to do with all the other bs drama
