Js 550 break down

[Ryan Declark]

I pulled apart this engine to reseal it and this is what i found. Cylinders are scored to piss and crankshafts are wobbly everything else seems to be fine. Looks like shes due for a couple sleeves. I think stock bore is 75mm and i want to keep it that way as its a 550 and i just want to get it to run. 550 is fun enough for what it is. I could do a 750 conversion on a SX model if i really want a fast 550 and with my tigercraft v3 hull rolling in at the end of the month this 550 is already taking more time and money than id like it too.

With that being said im due for a new crankshaft and i might as well do some pistons and rings in it too. The stock head was milled down by god knows who and when i last checked compression its was 175 rear/aft and 185 front/bow.(take a guess as to which cylinder has higher compression). So with that in mind does anyone have any suggestions as to which crankshaft and piston kit i should spend the money on. Keep in mind i just want reliability, if it costs me extra thats fine. Also anyone have a decent machine shop that can do a stock 550 sleeve that you recommend for SoCal area?

 

[Ryan Declark]

In depth

 

[WFO Speedracer]

What do you mean sleeves, it's a cast iron cylinder, no sleeves, IMO stay away from Forged pistons on a cast iron cylinder, you are already going to have to run a lot of clearance, no need to add to it.

Take that thing to a machine shop and have the bore checked, more than likely you will need to bore to the next oversize, at any rate you need to know that information before ordering pistons .

It has a lot of compression , the lip is milled completely off and it has the thick head washers so yes you can assume the head has been cut a lot . The problem is you won't know how much till you have it reassembled and run it to get the rings seated , it can vary quite a bit till the rings seat in . You could CC the head but I won't go into that here , look it up online there are some decent videos on that available. .

 

[Ryan Declark]

I have a 440 cylinder on the shelf. Fairly certain i get that sleeved at 75mm and its now a 550. Any added benefits from that aside from it not being vast iron?

 

[WFO Speedracer]

Yes you can resleeve the 440 Aluminum cylinder for 550 sleeves , I ran one for a few years , as a bonus you could probably run that cylinder with single cooling and forged pistons would be just fine , second bonus is you can set the piston to wall clearance up much tighter then with a cast iron cylinder .

I think the 440 Aluminum cylinder has two extra cylinder head bolts you have to drill out on the head , if you look at that 550 head you will see where they go , the bosses are there they are just not drilled out.

 

[Ryan Declark]

Do you have any opinions on the adr crank.

 

[WFO Speedracer]

Good cranks if you can get you hands on one.

 

[hornedogg79]

Your best bet is have competitive crankshaft rebuild yours... if you really need it. Rod play in the direction you are showing doesn't mean much. Pull up n down on the rod , not side to side. Are the bearings turning smooth? Looks pretty clean for a 550 crank.

 

[WFO Speedracer]

Truefully you would have to totally disassemble it , spin all the bearing and see what you have , if any of the bearings make noise they are done, if it's an outside bearing those can be replaced , if the inner bearing make noise it's crankshaft time. you should be replacing the crank seals anyway.

I have seen cylinders that look way worse than those but again, I bore gauge will tell you what is what.