How many Pistons do I have to ruin

[sledcrazyinCT]

A small "air leak" at a crank seal or an intake gasket will cause the usually perfect fuel/air mixture in the crankcase to become slightly lean...sometimes very lean. This lean mixture can quickly result in a seized piston. Air leaks are, by far, the number one cause of vintage engine piston seizures.

Air leak fables
Setting the carb slightly richer to accommodate the air leak can avoid a failure...wrong! Most air leaks draw a very minute amount of air at low engine speeds. In fact it's very common for air leaking engines to start and idle very nicely. However when the engine is brought up to full temperature at higher rpms, the castings will begin to expand and deflect slightly in different directions. At these higher temperatures the air intake of an air-leak can become many times greater. With this huge amount of additional air, even an "over-rich" air leaking engine will experience a critical lean condition after only a few moments of full load operation. This accounts for engines that run trouble free for years at moderate speeds with a low skill level rider, yet seize in the first few minutes of being run wide open by an expert rider. No amount of richness can effectively avoid the failure.

Air leaks can be accurately diagnosed without pressure testing…..wrong! Uneven or wavering idling is a common symptom of small air leaks on motorcycle engines. However in the case of vintage engines, only huge air leaks will result in rising and falling idle speeds. The majority of the smaller, yet equally destructive, air leaks will have no effect on idling. Another common practice of finding air leaks is the spraying of contact cleaner at potential leak areas while the engine is running. If the spray enters an air leak area, the idle speed will increase noticeably. This method is useful for large leaks in accessible places, however the majority of smaller hidden leaks can pass this test.... In short...it's a total waste of time.

Freshly rebuilt engines are free of air leaks…...wrong! Even engines that are rebuilt by the best technicians can air leak. About 20% of all freshly rebuilt engines will have small hidden air leaks. That's why most professional engine builders pressure test every engine before and after rebuilding. Installing fresh seals and gaskets is by no means a guarantee against air leaks.

http://www.klemmvintage.com/airleaks.htm

[loganm]

I prefer to keep discussions in PM form with one person at a time. Some of you post without reading through the whole thread, which is just the nature of the beast. I want to leave this thread open for discussion instead of closing it like the last one.

I have a question for the experts; smaller diameter needle is richer correct? I've said it before but, this is not a keihin needle, I ordered 3 different needles for comparison, I have a feeling this is from a Chinese scooter or something. If I'm running really lean in the first 1/2 of throttle no amount of cylinder boring or leak fixing is going to keep the motor from overheating.

[yaegerb]

Smaller diameter = richer
Steeper taper = richer

[loganm]

I'll work on finding the air leak tonight, after I get the aluminum off the cylinder walls and clean the piston up.

[AK47KID]

If you bore out an engine don't you have to rejet the carb? I'm asking Cuz I don't know

Sent from my SM-G935V using Tapatalk

[Scootertrash]

Dint take long.

[El Camexican]

http://www.menards.com/main/paint/so...4444212919.htm

Muriatic Acid. Dip a Q tip in it and rub it on the aluminum spot let sit for 5 to 10 minutes, wipe clean and repeat until all the aluminum is off the sleeve.

Yep, that one and don't forget to wear eye & hand protection and DON'T get a good breath of it, or you'll end up with a very sore throat. Be sure to wash the parts very well with water and dry afterwards (oil the steel) as the acid remains active for a long time after, even days if I recall.

[Scootertrash]

OP: Do you have a repair manual for this machine?

[El Camexican]

If you bore out an engine don't you have to rejet the carb? I'm asking Cuz I don't know

Sent from my SM-G935V using Tapatalk

Technically on a 2 stroke if you want your engine to run as well as it did before the bore you need to match the heights of your ports to what they were before the bore, so whether you do that or not you should still check your jetting after you break it in.

Another (and much more important) thing about proper jetting is that it is related to the content of oxygen in the volume of air passing through the engine at any given moment more so than any other factor. An example would be that today is 80F and you're heading up the mountains with your buddies. You find that your engine seems down on power. Next weekend you run out to the coast to ride in the sand and a cold front comes in. Your trike seems feels like it's on the bottle when you hit the power band even though you haven't touched a thing and your still using last weeks pre-mix.

The reason would be that you were jetted rich on the warm high altitude ride and NEAR perfect for the cool sea level ride. Now the scary part... THERE'S NO SUCH THINK AS PERFECT JETTING on a carburetor. But don't be scared. As long as everything else is good (no air leaks) and you aren't dedicated to 5 minute wide open uphill blasts or sub sea level air conditions your stock jetting should be fine for your otherwise stock engine after it's been bored. Keep in mind that your air/fuel screw is in effect an adjustable jet that you can play with at any time right on the trail.

The reason being that "close" jetting" is usually safe within 2,000' of corrected altitude change and almost every two stroke ever made (other than a few big bores) was overly rich to start with.

If you're planning to mess wit your jetting pull what you have in your carb and buy 2 sizes in both directions of the pilot and the main then read up on tuning and play with it. The rewards of proper jetting are better than adding a pipe, or adding fiber reeds, but be warned, power is addictive and it's hard to stop messing with jets once you get a taste of that power.

[loganm]

OP: Do you have a repair manual for this machine?

Even better, a service manual. In PDF form.

[loganm]

Pics of carnage. Went over the hot spots with some emery cloth, smoothed out the edges at oscarmayers suggestion.

Cylinder still has cross-hatching in it. Definitely not in it for the long run, but I should be able to get some rides/tuning out of it.

Yeah if I had the access to a machine shop I'd have the case halves checked for flatness and blueprinted, every mating surface machined, hell stroker crank and port work done to it. Financially it just is not a feasible thing, at that point may as well buy a brand new machine.

[JesseA420]

Even better

nope. same thing. LOL

just checked out your posting history to see if all your other threads are as goofy as this one. was not disappointed. keep up the good work.

[loganm]

Wrong. It's a factory service manual, which is MILES better than any Clymer POS.

Source: Anyone who's been turning a wrench for more than a day knows this.

[Scootertrash]

Funny thing, I have a Clymer or Haynes out in the garage for quick reference since I don't always have my tablet with me in the shop and it's done just fine for me

The tolerances and specs are the same in both. What more do you want?

Obviously the SERVICE MANUAL, (not the repair manual) isn't doing you any good, as well as having a "professional" shop do your machine work for you.

You bought a machine in rough shape, then:
You say you cleaned the carb, but yet you didn't verify the needle while apart? But you say you know your way around a carburetor?

Did your machinist have the piston when he bored the cylinder? If not, big mistake.

You force an "almost the same, but different" crank bearing into the case? Here's a ProTip for you: If an OEM bearing is not available, take the bearing to a bearing shop, they'll measure it and find you the right one.

You're dead set that there's an air leak, but you haven't even verified you have the proper components in your carb.

Whomever told you Wiseco was the problem is FOS. I use Wiseco exclusively and have had zero problems in my 40 or so years of wrenching. I have them in everything, or have put them in everything from atvs to snowmobiles to Harleys. Including when under the influence of a multitude if alterants when I was younger and dumber.

This whole fiasco with this build is ridiculous. You come here asking for help, then ignore the basics that are offered up by members here who have far more experience building motors than you.

Go back to square one:

If they didn't bore the cylinder to match the piston, take it back and have them fix it or find someone else to do it.

Make sure you have the proper carb, needle and jets for STOCK, or find out what they are and use that as a starting point for your jetting.

Read this thread: http://www.3wheelerworld.com/showthr...Jetting-Theory

Now, if you'll excuse me I have a transmsission out of a 1976 Harley FLH I need to tear apart. No dead blow s will be used in it's disassembly/reassembly

[loganm]

Funny thing, I have a Clymer or Haynes out in the garage for quick reference since I don't always have my tablet with me in the shop and it's done just fine for me

The tolerances and specs are the same in both. What more do you want?

Obviously the SERVICE MANUAL, (not the repair manual) aren't doing you any good, as well as having a "professional" shop do your machine work for you.

you bought a machine in rough shape, then:
You say you cleaned the carb, but yet you didn't verify the needle while apart? But you say you know your way around a carburetor?

Did your machinist have the piston when he bored the cylinder? If not, big mistake.

You force an "almost the same, but different" crank bearing into the case? Here's a ProTip for you: If an OEM bearing is not available, take the bearing to a bearing shop, they'll measure it and find you the right one.

You're dead set that there's an air leak, but you haven't even verified you have the proper components in your carb.

Whomever told you Wiseco was the problem is FOS. I use Wiseco exclusively and have had zero problems in my 40 or so years of wrenching. I have them in everything, or have put them in everything from atvs to snowmobiles to Harleys. Including when under the influence of a multitude if alterants when I was younger and dumber.

This whole fiasco with this build is ridiculous. You come here asking for help, then ignore the basics that are offered up by members here who have far more experience building motors than you.

Go back to square one:

If they didn't bore the cylinder to match the piston, take it back and have them fix it or find someone else to do it.

Make sure you have the proper carb, needle and jets for STOCK, or find out what they are and use that as a starting point for your jetting.

Read this thread: http://www.3wheelerworld.com/showthr...Jetting-Theory

Now, if you'll excuse me I have a transmsission out of a 1976 Harley FLH I need to tear apart. No dead blow s will be used in it's disassembly/reassembly

Verify the needle with what? What do I have to work with? Nothing. I got this machine not running. You're making a whole lot of assumptions, a lot of which is common sense stuff I addressed before ever making a thread.

FYI, I did not force any crank bearings into the case. The right side main shaft bearing is a "boutique" bearing commissioned by Honda and Yamaha. While the rest are readily available from bearing manufacturers, this one is not. Do some damn research before you post.

The machine shop bored and honed the cylinder to size with the piston, in fact they ordered it for me, I never saw it until picking it up. "Stock" jetting doesn't mean anything, especially on a 30 year old machine. Every machine is different for one, location (elevation, temperatures, humidity) have a lot to do with it.

Good luck on your Harley. It's dinosaur tech, so you shouldn't have a problem.

Edit: where are you even getting that I'm "dead set there's an air leak"? For the past two pages I've been saying I think it's the jetting. Also, I've read through that whole jetting article on another site.

Wrong about the plug chops, it can be black and still run lean, or white but still be fat. It depends on the oil, flash point, designed to burn off, etc.