cut the base on my 385xp on the bridgeport mill!

[Mattyo]

Ok, well, I won't lower the intake too much then. Would be really nice to see a photo of what I should do to the lower transfers. As is I might just polish them a bit rather than hogging them out.

We'll see what I end up with for compression, since I didn't cut the squish band... not that I can't.... maybe on the next saw

I won't bother getting a digital outside caliper then to check thickness on the cylinder... Just reshape a touch and polish and bevel. When I'm done, I'll recheck numbers.

Can I shave a touch off the flywheel key? to advance timing or grind the whole thing off and make a new keyway?

 

[Mastermind]

I just use a small file, and cut about 1/3 of the key away.

On the lowers....just remember, anything you remove will increase case volume, and decrease primary compression. I just radius the entry edges a little.

Now.......if you can building this saw to cut cants with a race chain, and a 16" bar........then all of my advice should be disregarded. I only build saws for work......and an 85cc saw should be built with a 28" - 32" bar in mind. At least to me that is.

 

[Freakingstang]

do you keep the stock carbs Randy, or do you do the 372XT carbs?

 

[Freakingstang]

Now.......if you can building this saw to cut cants with a race chain, and a 16" bar........then all of my advice should be disregarded. I only build saws for work......and an 85cc saw should be built with a 28" - 32" bar in mind. At least to me that is.

That's where differences lie... people want to compare short bar saws to long bar saw and each have their own strategy to get there.. I agree for me, a 85-90 cc saw is a work saw and will see big bars.

Some guys still do pop ups in the 385's, no?

 

[Mattyo]

I have an 8 pin rim for a 24" bar, and 7pin for a 28" bar. This will be a work saw....and bragging rights

 

[Mastermind]

I've tried every carb you can imagine. The XT carb works really well......but can be trouble prone. The early 390XP and the 385XP use a Tilly......that's probably the best carb for a worksaw.

That's where differences lie... people want to compare short bar saws to long bar saw and each have their own strategy to get there.. I agree for me, a 85-90 cc saw is a work saw and will see big bars.

Some guys still do pop ups in the 385's, no?

Some guys are only interested in doing a job as quick and easily as possible.......

 

[mdavlee]

385 with no gasket I think was 100 or 101 on exhaust.

I think the tilly has the best throttle response on them. I didn't try a xtorq carb but have an extra just in case something needs it.

 

[rmh3481]

Randy has a formula there that works. If you have access to a lathe and dont want to or cant cut the combustion chamber you can cut .030 off the piston crown edge to run a pop up piston. You can also cut .035-.050 off the intake side skirt. This gives you almost the same timing numbers. Set the squish tolerance first.

 

[Mattyo]

I've actually seen those vids before....thanks for reposting though. I figured i'd cut the case down to retain the gasket...i'll adjust the intake a touch, and smooth the transfers, but thats as serious as I'm gonna take this saw....

I do have access to a lathe, but its in a barn thats cold right now...not a fun place to be. So i'll stick w/ what I got, optimized squish and slightly tweaked intake timing...and I'm good

 

[Mastermind]

On the 390......a popup won't help you get that high exhaust down.

 

[Mattyo]

 

[Mattyo]

what do you mean, high exhaust? ie, a timing of 95 is too "high" and 105 is too low?

 

[Mastermind]

Exactly.

 

[Mattyo]

Thanks all for your help, gonna put it together and go for it I wasn't looking for a race saw...just a little extra is all... so lets see what I get! gonna go get those cabers installed and start assembly.... may even do a vac test

 

[Mattyo]

timing #'s

98/99
122
75

cylinder is on, and loctited down.... did a pressure/vac test and my methodology wasn't great, but the bearings do not leak...neither the cylinder head... only leaks from my blockoff points. so I think i'll press on...tomorrow it'll go mostly together hopefully!

 

[bluesportster02]

what do you mean, high exhaust? ie, a timing of 95 is too "high" and 105 is too low?

95means the ex roof is cut to hi you loose compression, 105 on this one needs raised some to get your rpm up

 

[Mattyo]

what am I missing? there isn't enough space between the clutch drum and the chassis to fit the chain brake......??????????? its uniformly tight all around. the SS brake binds on the chassis and the drum....so much so I can't even install the band...

never mind, answered my own question but figured I'd post just in case... chain brake mechanism needs to be installed BEFORE the clutch drum....got it

 

[Mattyo]

It's alive! 165 compression cold dry...fired up after only a few pulls. What a job getting this guy together!

Throttle response is excellent. ..thanks to all for the help!

 

[Mattyo]

asdfl;jasl;dfjal;sdjfl;ajsdl;fjal;sdjfl;j!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

gas tank leaks!!! saw came apart, back together w/ another tank... this one I pressure tested first! good thing I got that mitivac!

 

[Mattyo]

asd;lfkjasl;dfkjal;sdkfjl;akdfnvjksdnfgkl;jasdl;fjl;ksdfsdf ..... frustrating. Ok, saw together, starts nice, revs nice. Revved up...shut down. won't restart.

I still have compression, 160+ ... so hopefully nothing "let go" inside the cylinder. It pulls free.

Checked spark.... spark plug out and jumpered to the chassis... it sparks.

Pulled the carb apart and cleaned it.

Won't start.

I put some fuel down the carb...now it backfires and chuffs.

its scoffing at me....

I pulled the shutoff wire ground just to make sure its not that....

ideas?