What is my piston telling me ?

[Philodoxo]

Hi

I'm just a simple lawyer with absolutely no knowledge (quite common among lawyers) - not even on the engines.

I have a spare engine that I want to renovate - while I drive around on my XS400. That leaves me with 2 questions, that I hope you can tip me on:

1. Are the pistons so worn that I should Hone cylinder? Watch this short movie to see, what my piston is telling me. Click here

2. Does an engine with engine number 4G5-xxxxxx fit on my 2A2-xxxxxx bike ? They look just alike.

Hope anyone will vaste their time on an answer to me.

 

[eric123]

They look a little loose, you may want to measure to make sure. All XS400 SOHC motors will interchange in the motor mounts. I believe the XS250 and XS360 will as well...

 

[bentwrench]

Ah, a lawyer?

I can tell you exactly what's wrong.

My billable rate is $300 an hour. Please make an appointment with my secretary, and I can then look at your video.

 

[Philodoxo]

Hi bentwrench

I take it, that the bill is already sent ?

Working in public administration for a paltry wage without the ability to send bills to anyone ...... wondering why I chose that line of work

 

[HoughMade]

Well, welcome to another lawyer. I'm in private practice, but I'm just, in the last couple of years, seeing the fruits of my labor. Whoever said it, it seems true: "They don't let you make any real money 'til you are over 40." However, I think I would trade some income for not having to deal with some of the things I currently do.

...and by the way, I will agree that mechanical ability seems rare in lawyers, but I like to think I know a thing or two and I know a few others who can turn a wrench.

Anyhoo, as for changing over between a 4G5 and a 2A2 engine, in the U.S., at least, the basic engine is the same, but the 4G5 will have electronic ignition while the 2A2 will have points. However, it's as "easy" as picking which one you want and changing everything ignition related to it. It's not that tough a job. As for the crankcase, transmission, engine internals, jugs and head, they should be the same.

I can't view the movie for some reason, but perhaps a machine shop can give you the best idea as to whether new rings and a light hone would suffice or whether it's time to overbore, and get new pistons and rings.

Good luck!

 

[Arclight88]

Likewise on the viewing problem - please post another link.

Honing a cylinder is easy. Costs about $20 for the hone and use an electric drill. Follow directions to achieve a nice cross hatch pattern on your cylinders.

Agree on measuring for tollerances (which are listed in the online manuals.)

I look forward to progress reports.

 

[Philodoxo]

Does this link work better ?

https://picasaweb.google.com/lh/photo/Q31VjTYNGU7IDdMElxi-EtMTjNZETYmyPJy0liipFm0?feat=directlink

Anyway - I will measure and check the tolerance.

Thanks for the help.... so far.

 

[Arclight88]

Does this link work better ?

https://picasaweb.google.com/lh/photo/Q31VjTYNGU7IDdMElxi-EtMTjNZETYmyPJy0liipFm0?feat=directlink

Anyway - I will measure and check the tolerance.

Thanks for the help.... so far.

Thank you, that is a helpful video. The piston's movement inside the cylinder does not appear to be outrageously 'loose'. From an engineering stand point, the piston's jobs include (1) providing the mass reacting to the combustion cycle and (2) to provide the transport for the rings. It is the rings that do all the heavy lifiting from the standpoint of providing compression.

There is a tollerance for how worn a piston can be (and your measurements will let you know if they have reached the end of "useful life".)

Even engines with high milage can run on original pistons if they meet the specs. What is your bike' mileage? If it us under 30K miles, and the groove to ring clearance meets specs, and there are no obvious cracks, pits, or other damage, you may be just fine.

 

[Philodoxo]

Thanks - your answer is very helpfull !

Can't wait to meassure og look up the tolerance !