My thundercat - Page 2

Roflhat · 03 May 2014, 13:36

Quote:

Originally Posted by lukewhiting

There's some on eBay at the moment!

I'm Yet to go on a ribnet cruise! But I'm planning on it this summer

Hey Luke,
was checking out your youtube channel, nice vids there. Can I ask how you got songs on them? I thought there was some copyright issue?

Born in '94, good year

lukewhiting · 03 May 2014, 22:22

Quote:

Originally Posted by Roflhat

Hey Luke,

was checking out your youtube channel, nice vids there. Can I ask how you got songs on them? I thought there was some copyright issue?

Born in '94, good year

Just used windows movie maker. They songs loaded straight on when on YouTube no troubles. I've found a few songs that are new out it won't work but after a month or so it's fine

Roflhat · 08 June 2014, 08:40

Started taking apart my engine today, got it completely stripped down today and got a few things done.

Started with basically a stock engine - boyesen reeds, exhaust mod, lighting coils removed and nukaru coils.

Plan is
Get the crank welded
Get the crank/flywheel balanced
remove flywheel ring gear
get the head shaved 1mm
polish pistons, head, ports etc.
yamaha 70 carbs
D1 exhaust tuner
BR8 HIX plugs - Think these are correct for a shaved head?
Mikuni triple fuel pump (reliability not performance)

Here's the coils:

Here's the yam 70 carbs next to the standard D2 carbs:

They're the square bowl type. Very tight fit on the tohatsu! Had to shave a bolt to get them to squish together enough. Think these are automatic choke? Not sure how I'm going to the get that to work...

Another small problem - the 50hp carb bolts are too short, so I've had to order 90mm long ones.

I was speaking to fast fred before I started so I knew this one -

You have to use the link from the tohatsu 50 on the 70 carbs. The 70 ones aren't adjustable whereas the 50 ones are.

Another small job -

You can see the step at the back of the carbs, to take advantage of the extra diameter of the 70 carbs you have to open up the reed block.

Roflhat · 08 June 2014, 08:43

Next the powerhead came off -

Continued to strip it down, first time taking an engine back this far -

Pistons before polishing -

After -

Started wtih 240 grit sand paper then 500 then 2000.

The cylinder head got the same treatment -

Roflhat · 08 June 2014, 08:44

Had a go at some mild porting -

Think I'm going to open them up some. The top one here is stock, the middle is after I smoothed it. They had very rough edges when I started and they're already much smoother, but not much larger. Thoughts on this?

Roflhat · 08 June 2014, 08:46

Got the flywheel done, weighed 3.42kg to begin with, 2.96kg after. Not much less but all the weight removed was from the outside edges so it has more effect.

Just used a grinder to cut almost to the centre part of the flywheel, the used a hacksaw to finish it. Just popped apart, simple as.

(the tape is to stop anything getting on the magnets)

Job done

Roflhat · 08 June 2014, 08:47

Gave the block a clean -

Used the parts washer first with Jizer then pressure washed them

Going to get some primer, not sure what colour to go for yet.

Looking a bit empty back there -

spartacus · 08 June 2014, 09:01

Good job. Any broken bolts so far in strip down?

lukewhiting · 08 June 2014, 10:21

Got a first judge of top speed the other day. Raced a jetski that topped out at 55mph on his speedo & I must of been doing a good 3-5mph faster with two up & 20ltrs of feul.

Do you recon take the outer ring off the flywheel will make much difference?

Roflhat · 08 June 2014, 13:31

Quote:

Originally Posted by spartacus

Good job. Any broken bolts so far in strip down?

None surprisingly! Was very straight forward so far, got to love these 2 strokes

Roflhat · 08 June 2014, 13:33

Quote:

Originally Posted by lukewhiting

Got a first judge of top speed the other day. Raced a jetski that topped out at 55mph on his speedo & I must of been doing a good 3-5mph faster with two up & 20ltrs of feul.

Do you recon take the outer ring off the flywheel will make much difference?

That's pretty good going, that prop you've got must be a nice one. Is your rev limiter still intact?

It doesn't make that much difference to top speed, maybe a tiny bit. Mostly acceleration, helps when you're jumping waves and when it's choppy, especially running bigger pitch props.

lukewhiting · 08 June 2014, 16:56

Quote:

Originally Posted by Roflhat

That's pretty good going, that prop you've got must be a nice one. Is your rev limiter still intact?

It doesn't make that much difference to top speed, maybe a tiny bit. Mostly acceleration, helps when you're jumping waves and when it's choppy, especially running bigger pitch props.

I like it! Getting reconditioned soon so I can find out what pitch it is then. Yeah I believe everything is race ready so not really changed much.

Might have to give it a go then!

Peter_C · 08 June 2014, 17:08

If I may, I would recommend continuing to polish the head, and the pistons until they are a mirror. This will help keep the carbon from sticking, which can cause pre-detonation. Use a 2-3 inch polishing pad on a straight or angle die grinder with some polish. Should only take a few minutes on each one. Wash them really well after.

That is a major undertaking for a first time tear down. Organization is the key to success, and as long as you reverse your disassembly procedure you will do just fine

Roflhat · 08 June 2014, 18:51

Quote:

Originally Posted by Peter_C

If I may, I would recommend continuing to polish the head, and the pistons until they are a mirror. This will help keep the carbon from sticking, which can cause pre-detonation. Use a 2-3 inch polishing pad on a straight or angle die grinder with some polish. Should only take a few minutes on each one. Wash them really well after.

That is a major undertaking for a first time tear down. Organization is the key to success, and as long as you reverse your disassembly procedure you will do just fine

thanks, all advice much appreciated! Feedback is always good, I'm trying to do it right first time so the engine lasts.
I'll do that on tuesday, away tomorrow. The crank and head are going over to town tomorrow to get done.

I've taken hundreds of photos as I go along, hopefully I can figure it out! My dads giving me a hand as well.

Roflhat · 08 June 2014, 19:03

Managed to snap two bolts today taking apart the engine mounts. Got the old exhaust out and the new one on. The original was 270mm long and 39mm wide, new one is 260mm long and 48mm wide. Apparently gives better top end.

Also opened up the exhaust ports some more (top one is from yesterday, middle is towards the end of today)

Did some polishing and cleaning up on the intake/ front half of crank case

Then started on the back half of the crank case. You can see the casting imperfections here -

Removed -

Smoothed off the sharp edges -

Still needs to be polished -

I tried to keep the work done equal for all cylinders

Roflhat · 13 June 2014, 21:57

Bit of an update.
Crank has been welded. Before -

After -

Reef block has been opened up -

Really nice job done on it, very pleased.

Roflhat · 13 June 2014, 22:03

The final ports look like this -

I polished this bit too, the cover for the exhausts -

Roflhat · 13 June 2014, 22:09

Had 1mm removed from the cylinder head, was 33.6mm, now 32.6mm. Should increase compression by 30psi. Was at 140psi before the rebuild.
Again a really nice job done on it. I polished up the head as well as the pistons. The photos don't really show up how shiny they are.

Also drilled and tapped a hole for the pulse feed for the new fuel pump, a Mikuni triple outlet from a 3cyl jetski. More of a reliability upgrade than performance - the Tohatsu one isn't too great.

Roflhat · 13 June 2014, 22:13

Started putting everything back together, crank in, case halves together, everything torqued up. Block ready to go -

Primer -

And Paint -

Painted the recoil cover as well -

Roflhat · 14 June 2014, 17:03

Spent today getting the engine together and back on.

Using a fuel pump from a yamaha 30 just now, waiting for a fuel barb for the mikuni pump.
Having problems with the carbs and the throttle setup from the tohatsu not wanting to work together. The way the linkage on the yam carbs is means they're at almost wide open throttle when the tohatsu tiller is at idle.
Took off the carbs to compare, not quite sure how to sort this?

The roller on the top LHS of the carb is the problem.
I've tried taking the assembly from the 50 carb over to the 70 but it's much shorter and won't work. Can't see an obvious solution other than welding the 50 setup onto the 70 one?