Hello, my blaster has for the last few years only started by being pop started behind another machine. Could kick and kick and would usually never start it. Finally did a compression test, only getting about 90. Took apart the top end, and found a few things. 1- The cylinder walls appear smooth with no damage to them. 2- the piston does seem damaged. It looks like pieces from the bottom of the piston have broken off. I don't see any pieces under the top end though? Any thoughts? Was thinking about sending it out to full bore for boring and new piston and parts, no good machine shops in my area, but if the cylinder walls appear undamaged is this necessary? Thank you.
Blaster Top End Job Questions
- Thread starter Dczym
- Start date
A broken skirt is usually caused by piston slap from a worn piston and to much clearance. It seems this is what has happened in you're case.
1. Make sure you check you're crank and cases. Broken skirt often takes the crank and or cases with it.
2. The jug needs to be measured to figure out what bore size you are at. And how much you will need to go out to. You're machine shop can do this for you. If you dont have a local trustworthy machine shop send it to o'connor racing he can bore it and order the correct piston for it and send it back to you.
Qhen you put it back together make sure you do a leak down test.
1. Make sure you check you're crank and cases. Broken skirt often takes the crank and or cases with it.
2. The jug needs to be measured to figure out what bore size you are at. And how much you will need to go out to. You're machine shop can do this for you. If you dont have a local trustworthy machine shop send it to o'connor racing he can bore it and order the correct piston for it and send it back to you.
Qhen you put it back together make sure you do a leak down test.
Alright thank you, is it difficult to take apart the crank case to check? Anything to pay specific attention to? This is my first time doing any serious work like this by myself. Thank you!
Cracked cases will be obvious from the metal pieces of the skirt getting jammed in between the crank. The crank itself make sure the big end of the rod does not have any up and down play.
Pull the crank to tdc and hold it push and pull on the rod. If there feels like there is any play then it needs to be replaced. Rotate the crank with your hand if it is tight this would likely mean main bearings are toast. You do not have to split the cases to inspect but if its damaged then yes you do.
I would HIGHLY RECOMMEND you get a service manual as this will probably be you're most valuable tool.
Once you have figured out what you need to replace and you get it all back together make sure you do a leak down test as an air leak will ruin the engine you just spent money and time on in a hurry.
Pull the crank to tdc and hold it push and pull on the rod. If there feels like there is any play then it needs to be replaced. Rotate the crank with your hand if it is tight this would likely mean main bearings are toast. You do not have to split the cases to inspect but if its damaged then yes you do.
I would HIGHLY RECOMMEND you get a service manual as this will probably be you're most valuable tool.
Once you have figured out what you need to replace and you get it all back together make sure you do a leak down test as an air leak will ruin the engine you just spent money and time on in a hurry.
If not splitting cases. Make sute you get out any and all peices of the skirt. Or damage can occur. If not already. Smaller pieces can get in crank bearings
New piston, new bore.
Piston and bores are maintenance items on a 2t.
Lack of maintenance leads to excessive clearances between piston and cylinder lead to broken skirts.
Like mentioned above.
Forged pistons take more abuse and general the skirts don't break off
New piston, new bore.
Piston and bores are maintenance items on a 2t.
Lack of maintenance leads to excessive clearances between piston and cylinder lead to broken skirts.
Like mentioned above.
Forged pistons take more abuse and general the skirts don't break off
