87 Jug issues. Need guru assistance.

[Goat]

I've got a 87 engine that I just finished putting in a quadracer 250 frame. Finished it last Sat. Been having jetting issues all week. Found a problem with the jug tonight. Rear jug to case mounting points where the nut goes on the stud. Between the nut and jug there is a crack on both left and right mounts. I noticed it because it was oozing premix. Haven't tore the engine down yet. I'm guessing that the intake ports are right behind those studs? Can the cracks just be welded up and be ok or should I be looking for a new cylinder? I can get some pics if that helps.

[sandblaster]

Goat!
Haven't heard from you in a coons age!
Yeah, post some pics.
I've seen some crazy stuff welded up on cylinders so probably.
Welcome back.

[Goat]

Haven't been on the internet much in the past year. Been too busy working, riding my 95 CBR1000F, and building another quad

How have you been?

Pics will be up shortly.

[Goat]

right side


left side


right side


Couldn't get a better angle of the left side without removing the pipe. Cracks are about an inch long. I'll remove the pipe tomorrow if needed. Quad is in prototype right now. wanted to make sure the frame didn't need any reinforcement before I powder coat it. I'll make a build thread for it one of these days.

[motopunk]

oh looks bad, but with a good aluminum welder can the cylinder to be repaired. You should also check the crank case and the cylinder base. sometimes it's a bad old gasket or to over-tighten the nuts, which caused those cracks or breaks.

[sandblaster]

Here's a view looking down the intake.
I guess you won't know for sure until you get it apart...

[Friar-Tuck]

 
Headstay stress?
Tuck\o/

[alward25]

I have welded them, just make sure you check the base for straightness after.  Welding can warp the ear.  +2 on the headstay stress. +2 on the cases too

[Goat]

I do have pretty beefy engine mounts. It vibrates the whole quad quite a bit. Way more than in the K5 frame. I think I'll put rubber spacers/washers in all the mounts now.

I will start tear down this weekend and take more pics of the damage. Judging by sandblasters pic it looks like it's cracked in the cylinder. I hope not I wanted to do a complete rebuild through winter not summer.

Thanks for the help guys.

[Goat]

Never had this engine apart before. Got the jug off and found out it has a LA Sleeve installed. Everything looks pretty good. It looks like the cracks are on the top edge of the intake ports but not 100% sure. Can't really see in the ports at the right angle to see if its cracked in there. Without the jug bolted to the trans it's hard to see the cracks on the outside. Waiting for a couple welding shops to call me back.

I hate not having the tools to do the job myself. As soon as I figure out where I'm taking it to get welded up I will media blast the whole jug and get it clean to save money at the welder. I've heard there is an 8 hour window with aluminum before it would need re-cleaned to weld properly. I'm also going to ask about getting new power valves made. Could they be made out of steel? Mine are still in good working order but the teeth are showing some wear and would like to have them made before the teeth are gone.

Crank, rod and piston pin bearings are well within spec so I will wait on tearing the whole engine apart for the moment. When I do a complete rebuild I want to do some mods. Window piston, porting, get the head reworked and milled a little, maybe even crank stuffers.

[yeomans]

You can find stock steel valves for the early 500's.
I have both steel and aluminium oem sets.
Just cant seem to find out any info on how to i.d which year cylinder they came from. 86, 87, 88?