Jump to content

Need help with jr 80 think it needs a piston

Recommended Posts

Was smoking a lot and wouldn't idle so I cleaned the carb put it back together bike ran ok but was still smoking a lot decided to take it out after about 5 mins bike died while driving it started up again but couldn't build revs just died even with the throttle open just died slowly any advice would be brilliant thanks

20181020_015507.jpg

Share this post


Link to post
Share on other sites
11 hours ago, Connor Hughes said:

Was smoking a lot and wouldn't idle so I cleaned the carb put it back together bike ran ok but was still smoking a lot decided to take it out after about 5 mins bike died while driving it started up again but couldn't build revs just died even with the throttle open just died slowly any advice would be brilliant thanks

20181020_015507.jpg

 

Does this one have a Cast Iron cylinder most likely order the next size and take it to have it bored to match. Blowby on the piston so it needs a new top end, is the bottom end still tight?

Share this post


Link to post
Share on other sites

 

 

2 hours ago, ar2stroke said:

 

Does this one have a Cast Iron cylinder most likely order the next size and take it to have it bored to match. Blowby on the piston so it needs a new top end, is the bottom end still tight?

How would go about the checking the bottom end.not to sure if the cylinder is cast iron ,theres a little play forward and backwards when looking at it from the angle of the picture if that's what you mean .

Edited by Connor Hughes

Share this post


Link to post
Share on other sites
Just now, Connor Hughes said:

 

 

How would go about checking 

So the bottom end is checked with a feeler guage (should be zero up/down play).

The side-to-side clearance is checked what year and model is this JR80?

thanks

Share this post


Link to post
Share on other sites
31 minutes ago, ar2stroke said:

So the bottom end is checked with a feeler guage (should be zero up/down play).

The side-to-side clearance is checked what year and model is this JR80?

thanks

not to sure if the cylinder is cast iron ,theres a little play forward and backwards when looking at it from the angle of the picture if that's what you mean. So what would have caused the blowby the piston had been rubing on the cylinder also does this mean the bottom end needs work.(I've not long bought the bike, I think the previous owner might have put a smaller piston in by mistake this possible.)20181020_164617.thumb.jpg.9f3c6ddf96faaffb144606ed842d65ed.jpg

20181020_165112.jpg

20181020_165001.jpg

20181020_164628.jpg

20180918_224022.jpg

Edited by Connor Hughes

Share this post


Link to post
Share on other sites
9 minutes ago, Connor Hughes said:

not to sure if the cylinder is cast iron ,theres a little play forward and backwards when looking at it from the angle of the picture if that's what you mean. So what would have caused the blowby

Blowby is just the rings worn from hours on the bike.

The bottom end side to side clearance is a separate item to check, just get the year/model and use a feeler gauge to see if it is in spec.

  • Helpful 1

Share this post


Link to post
Share on other sites
12 minutes ago, ar2stroke said:

Blowby is just the rings worn from hours on the bike.

The bottom end side to side clearance is a separate item to check, just get the year/model and use a feeler gauge to see if it is in spec.

Take a look at what I've put earlier it's been edited and put up a few mkre pics. would the blowby cause the piston to rub against the cylinder or is that why I need to check the bottom end and thanks for your help with this really appreciate it.

Share this post


Link to post
Share on other sites
27 minutes ago, Connor Hughes said:

Take a look at what I've put earlier it's been edited and put up a few mkre pics. would the blowby cause the piston to rub against the cylinder or is that why I need to check the bottom end and thanks for your help with this really appreciate it.

The bottom end check (is not going to have any impact on the piston rocking in the cylinder). It is kinda standard practice to check the 'side-to-side' clearance of the bottom end when the top end is off.

Most likely what you see on the cylinder is from the piston rocking/slapping the cylinder what year is this bike?

Share this post


Link to post
Share on other sites

Your going to have to wash your bottom end out real good as I see a lot of debris from pulling the Piston and cylinder fell into it. Next size piston and rings with a fresh bore is definitely recommended to judging from the amount of leakage past the rings. It would be a good idea to put new crank seals on as well, as the run-time it appears is on your bike has likely damaged those as well. That could have been the reason that it slowly died as it did. A little troubleshooting prior to pulling it apart could have answered that up front. But if you put a fresh top end on it without washing the bottom end out you could lunch the fresh top end and the crank bearings as well.

  • Like 2
  • Helpful 1

Share this post


Link to post
Share on other sites
On 10/20/2018 at 5:40 PM, ar2stroke said:

The bottom end check (is not going to have any impact on the piston rocking in the cylinder). It is kinda standard practice to check the 'side-to-side' clearance of the bottom end when the top end is off.

Most likely what you see on the cylinder is from the piston rocking/slapping the cylinder what year is this bike?

Its a 2006. so what's caused the piston to rock/slap the cylinder .

Share this post


Link to post
Share on other sites
1 hour ago, Connor Hughes said:

Its a 2006. so what's caused the piston to rock/slap the cylinder .

It is a Case iron sleeve from looking at the parts diagram they wear oval. When the piston/rings wears from not being replaced (here it slapping) the cylinder it causes that wear you see.

Looks like you will need to order the next size piston and have it bored to fit. Make sure the Air Filter is good (no tears/rips) in the seems and air boot is clean as well.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×