MB100 development

**flyingbrick** · 18th November 2018, 08:40

Thanks mate. Appreciate it.

If i could swing another 600 past the wife (the cost of initial bike purchase again) id have a spare engine to build and a 6 speed box.. doh.

What do i have here to sell....

**flyingbrick** · 18th November 2018, 08:43

I'll slip some solder in the plug hole to measure squish.. saw that on a youtube channel,

would you consider that small increase in CR Worthy of a jet change? I know nothing about anything so learning lots as i go

**flyingbrick** · 18th November 2018, 09:03

Sorry about flooding with posts. Do these photos tell anyone anything worth knowing?

**speedpro** · 18th November 2018, 09:11

The head tells me either the chamber and squish band is not concentric with the cylinder or someone has machined it on the piss. There is also signs of blowby on the gasket surface, more obvious on the cylinder. That clean region in the squish says the piston is getting real close. That will need to be sorted out so it is even all around before you remove the gasket. Once you start getting the compression up over 12:1 or so even very small changes in chamber volume have a big effect on the compression ratio. As Dave said things need to be measured carefully. With the less than ideal porting and pipe you could probably go to something close to 14:1, depending on what else you do.

**F5 Dave** · 18th November 2018, 09:15

And be on gas 95 min.

**flyingbrick** · 18th November 2018, 09:24

Thanks all. According to the last owner this thing hasnt been worked on since purchased in 91 and one lady owner before him

so could be factory machining?

I have cleaned everything up and will re assemble with the same gasket to get me riding again.

Will throw some master gasket in there to try stop the leaks and will use a torque wrench. Are factoey tq specs good? I have it listed in manual as just 14-17 ft-lb...seems low?

**flyingbrick** · 18th November 2018, 09:29

Also.. the intake and side ports are lower than pistol at bottom dead center.

Could i move gasket to bottom of cylinder? This would raise ports (i hear this is good) but keep squish up top the same?

Sorry if a rediculious question

**flyingbrick** · 18th November 2018, 10:37

Took one squish reading. 1.04mm. enough to tell me i need to keep the gasket haha.

Im surprised how close it is already!

**F5 Dave** · 18th November 2018, 10:48

Yeah that's not std I'd bet.

**Ocean1** · 18th November 2018, 10:58

Originally Posted by flyingbrick

I have cleaned everything up and will re assemble with the same gasket to get me riding again.

Will throw some master gasket in there to try stop the leaks and will use a torque wrench. Are factoey tq specs good? I have it listed in manual as just 14-17 ft-lb...seems low?

I found straight silicone is better than master gasket with a used head gasket. Degrease everything and just wipe a thin smear over both sides. Seals up the minor imperfections usually dealt with by the coatings they put on a new gasket, and it's good for the high temperatures.

And whatever torque is in the book is better than any guess you'll make, so unless someone's got a bunch of empirical data to the contrary why would you fuck with it?

**flyingbrick** · 18th November 2018, 11:51

Thanks ocean1.

Have seen many times over the years experienced people specifying different torque values over factory suggestions.

Its all together now and torqued to factory specs in the suggested order (although i did take it to full torque in a few passes)

I used a smear of 518 as ita supposedly better on aluminium than the 515 i also have. I hate silicone and wish i didnt even have to use it in the bathroom.

Want to dive head first into a full rebuild and porting but like riding it too much :-D

**flyingbrick** · 18th November 2018, 11:58

Oops double post

**TZ350** · 18th November 2018, 19:36

Originally Posted by flyingbrick

Do people space up mb cylinders to raise the ports? (And machine top of cylinder)

1. Space the cylinder so the transfers are in the right place.
2. File the exhaust port so its timing and width are in the right place.
3. Boysen port the inlet and cut the piston skirt so the inlet timing is in the right place.
4. machine the cylinder to get the deck height in the right place.
5. "O" ring the top of the cylinder, a 2mm thickness Viton "O" ring makes a great head gasket.
6. Skim the head and angle the squish to match the piston.
7. CC the head.
8. 0.6mm squish clearance, checking with solder I go for 0.8 and figure it will be 0.6. Crank is bendy.
9. Don't open up the exhaust duct, they are usually to big from stock.
10 The exhaust duct at the exhaust flange should be 95% of the area of the single exhaust port. much less for triple exhaust ports.