The joy of seeing your bores at 3000 miles...

[AAAltered]

My motor is about 6 years old and 3000 miles.

Since I'm pulling the lump from the frame, I took the heads off and got to examine my domes, pistons, and bores.

Big relief,  they look really good to my eye.  Lots of oil.  No obvious seizes.  Heads no sign of detonation.  Piston crowns I can't read but appreciate any input.  I do see some vertical lines in one bore but they are smooth and doubt it's anything but normal.  Makes me feel good.  What geeks we are.

Time to unbutton:



Left cylinder and head:







Right side:

[m in sc]

not bad, looks like some blow-by going in. 

[AAAltered]

These heads were shaped and squished by SCR years ago.  Can I get them oringed without changes to the jugs?

[m in sc]

you'll reduce head volume too much. Id either run it or send it to chuck for a once over.

[paul1478]

Man I love those DG heads.

[SUPERTUNE]

I don't see any headgasket leaks or failures. I would leave as is, no need to spend a bunch of money going to o-ring setup and is for racebikes that get changed often. They hold up better in the watercooled engines than the air cooled engines IMO.

On another note...just did a topend job and put new pistons in Guillermo's RD400 TSR STG 2 build after 8000 miles and was able to do just a clean up hone and put in a fresh set of Wiseco pistons and rings and ran great!
Chuck

[Dvsrd]

I don't see any headgasket leaks or failures. I would leave as is, no need to spend a bunch of money going to o-ring setup and is for racebikes that get changed often. They hold up better in the watercooled engines than the air cooled engines IMO.

On another note...just did a topend job and put new pistons in Guillermo's RD400 TSR STG 2 build after 8000 miles and was able to do just a clean up hone and put in a fresh set of Wiseco pistons and rings and ran great!
Chuck

Chuck, did you specifically use Wiseco because they use a larger piston clearance? Obviously assuming the pistons measure the same as alternative cast pistons.

[SUPERTUNE]

Most piston and ring manufacturing company's use OEM standards to make parts fit.
If Yamaha states the bore is 64.00, the piston and ring parts are made to fit in that size of bore.
When bored oversized lets say 65.50mm the piston clearance is built into the piston sizing, so a cast Pro-X may have .0018 clearance, but a
Wiseco forged piston will measure .003 clearance in the same bore. A forged piston will need more piston the wall clearance to expand.
This way Piston Ring tolerances can be followed! IMPORTANT!
For every .001in bore size larger, the ring end gaps will get bigger times PI, which is .00314

I have found through 35 years of building RD aircooled engines I do set the piston to wall clearance for the job, type of piston, what bore the piston is and what brand piston is.  OEM Yamaha, Pro-X(Banshee), Wiseco, and Wossner are all different piston clearances.

Example....If I bore a stock RD 350/400 1st over @ 64.25mm with a Pro-X banshee piston and the bike is stock I'll set piston to wall @ .0019 for today's fuel. (never follow stock spec's unless your going to use canned race fuel)
If the RD is a hotrod, cut heads, aftermarket heads with pipes I'll be .0022
If the same mods but at 65.75mm bore I'll set clearances to .0025 for the thicker pistons that will need more running clearance.

Wiseco and Wosser pistons will follow suit, but using greater clearances due to being forged pistons.
No need for a Wiseco/Wossner forged piston in a stock bike unless a race bike like a Historic Production Class that will have the snot ran out out it for everything it will give you...
stock and update porting engines builds Cast Pro-X are fine.
Most of my stg 1 builds it's optional on cast or forged pistons, with stg 2 and up to full race porting, I only use forged pistons and even do
piston coatings to strengthen them of to be more fool proof ( like opp's I missed the jetting this morning and didn't hurt it in practice)

In Guillermo's setup @ 66.25mm bore, using uncoated pistons, it's perfectly happy at .0035 with a good warm up before a taxing run.

Chuck

[Striker1423]

Very informative Chuck! I don't want to but I'm at around 1500 miles on my top end. Once the bikes back.together and I hit 3k, maybe I can make a follow up post to this to compare.

I have a feeling mines not gonna look so sweet lol.

Chuck, do you drill the Wiseco recommended oil relief hole at the exhaust bridge? Cause... uh I didn't. A friend asked me if I did as per the Wiseco instructions and I laughed nervously.

[AAAltered]

Yes very informative, thanks.

FYI this top end is an R5, with HVC *cast* pistons, 3rd over.  When built in 2013, 202 and I discussed what pistons to use and since HVC had only recently commissioned those pistons I wanted to try them.

I think the bores were done by powerseal, although there was another PA company that 202 also used that I think is out of business.

I like the idea of cleanup and go, given that I have a long shopping list and a budget.  For this bike, There's plenty of was to improve without doing anything to the Motor.  If you recall, I finally had it running at top notch before the tear down.

I'll be spending on chrome, rubber, cables, etc.  I made a big list over winter and now that I'm back to "hands on", disassemble  and cleaning I am honing my list and maximizing value of the spend.

Stay tuned.

Ed

[teazer]

Nice combustion chamber shapes.  Not original DG profiles as was mentioned.

[paul1478]

I don't see any headgasket leaks or failures. I would leave as is, no need to spend a bunch of money going to o-ring setup and is for racebikes that get changed often. They hold up better in the watercooled engines than the air cooled engines IMO.

On another note...just did a topend job and put new pistons in Guillermo's RD400 TSR STG 2 build after 8000 miles and was able to do just a clean up hone and put in a fresh set of Wiseco pistons and rings and ran great!
Chuck

Ok so the fact of the thread is 8000 miles.
8000 miles.
On a RD.
In 2 years ?
Wow Guillermo! Hats off to you sir.

[Czakky]

@Paul and Chuck, No kidding! I have to ask, what oil is he using...?

[SUPERTUNE]

Very informative Chuck! I don't want to but I'm at around 1500 miles on my top end. Once the bikes back.together and I hit 3k, maybe I can make a follow up post to this to compare.

I have a feeling mines not gonna look so sweet lol.

Chuck, do you drill the Wiseco recommended oil relief hole at the exhaust bridge? Cause... uh I didn't. A friend asked me if I did as per the Wiseco instructions and I laughed nervously.

Matt, No bridge exhaust port in an RD air cooled engine...not even in a RZ/Banshee cylinder... so no need to drill holes in the piston skirt!
You pulled that one off by making faces at him as he's dummer than you....
C

[SUPERTUNE]

I don't see any headgasket leaks or failures. I would leave as is, no need to spend a bunch of money going to o-ring setup and is for racebikes that get changed often. They hold up better in the watercooled engines than the air cooled engines IMO.

On another note...just did a topend job and put new pistons in Guillermo's RD400 TSR STG 2 build after 8000 miles and was able to do just a clean up hone and put in a fresh set of Wiseco pistons and rings and ran great!
Chuck

Ok so the fact of the thread is 8000 miles.
8000 miles.
On a RD.
In 2 years ?
Wow Guillermo! Hats off to you sir.

Get that fancy paint job done, you have some catching up miles to do!!
I know we had a problem with some headbolts not holding torque on your STG 2, hence we did have the top end off last December to put in new base gaskets, and yours looked perfect still...don't remember how many miles you have since the build?
Chuck