Simmy's Naked Turbo Project

Vacuum while cutting.

 

The 650 turbo cases have 75 mm holes.
The outside diameter of the 900 (67mm) cylinders is 72.5 mm so lots of clearance.
The battery was dead in my digital calipers but it appears the 900 block and the Turbo block are both around 77 mm height.
I was not expecting this, I need to get a new battery so I can take more precise measurements.
It also appears that both motors measure 90 mm from the crank centre to the top of the cases.
900 pistons are quite a bit shorter than the Turbo's.
Turbo has a thicker metal base gasket. 900 has typical thinner fiber base gasket.
As I dig deeper I'll compare the rods.
I suspect the 900 barrels may need to be shimmed higher to achieve 8.2:1 CR.
A 738 might be easier to build than I thought.

 

You need a dial caliper so you don't have to rely on batteries.

 

I put the 650Turbo piston and the 67mm piston together with the same wrist pin.
This makes a visual comparison easy.

 

900 and Turbo wrist pins

 

Putting my junk motors aside for the moment I thought I would try tuning my carbs again only to find #1 refuses to fire at all on the idle circuit.
Being #1 I had access so I removed the mixture screw and pulled the throttle slide.
I tried a last ditch effort and sprayed carb cleaner where I could. No dice, no fire.
I verified it has good spark and even changed the plug with #4.
Unfortunately I will have to pull the carbs back off to deal with #1 again.
Good thing I'm in no hurry, very disappointing though.
But hey, on the positive side 3 of the 4 are performing great.
I know it kicks in on the mains and runs then.

 

You can sneak the #1 carb bowl off and get the pilot jet out with a 90º ratcheting screwdriver and the appropriate bits.

If you're good at pulling carbs it's not worth the effort though.

 

I wouldn't say I'm good at pulling carbs, these were a real bitch to install.
This is very tempting but I think its gonna need another soak in the ultrasound tank.
I had them vapour blasted after the ultrasound last time, maybe this left sand behind.
I did rinse and blow them with air after.
Have a look at this guy's video. I love how he flows the fluid through.
This video has a language alert.

https://www.bing.com/videos/search?...os/search?q=cleaning+mikuni+carbs&FORM=HDRSC4

 

Vapor blasting uses baking soda or other water-soluble media.

 

OK that is good to know.
I'm not going to use the same WD40 brand cleaner from last time. That left the aluminum black.

 

I finally stopped feeling sorry for myself and got at the carb removal.
It took me about 2 hours to get the carbs on the bench and #1 isolated.
The fuel pump, fuel regulator, battery box, air filter, surge tank all have to be removed.
So far I removed the idle jet and blew it through with air. Its possible it was plugged since a small grain of dirt is seemingly all it would take.
I really don't want to be removing them after this time.
Does anyone have any suggestions what I can do to positively ensure the idle passages are clear on this carb?

 

Remove all rubber seals and soak in Berryman's Carb Dip for 2 hours,

Alternatively (and less certainly) blast the hell out of the idle circuit with your favorite carb cleaner.

 

When the carb cleaner shoots you in the eye you know the passage is clear.

 

Vapor blast Canada guy here in Chilliwack uses glass beads. I think that’s why the carbs look like new as the beads polish the aluminum.

 

I tried finding this Berryman’s stuff about a year ago, nobody seems to sell it in Canada.

 

Just had a look and Amazon.ca has it at a BIG price 127$
Or autozone for $29.99
I’ll have the in-laws pick up a can in Bellingham for me.

 

ya I suspect that is what was used, he told me to rinse and blow them real good.

 

nice, do you know if it will tarnish the beautiful finish it has now?

 

As far as I can remember we used that many years ago in the shop and never had a problem.

 

Only if you let it sit for too long. An overnight soak will make it look like it was anodized grey, but the finish might not be even.