250 1988 yz250 build

L

Lovespeed

Alright just checked out the boot Between the carb and the engine and noticed one of the screws was missing out on the boot. Could something small as that cause an air leak? It seemed to be sealed but maybe not. Also when I took the boot off I noticed liquid between the boot and plastic thing (idk what it's called) so maybe air was getting in through there?
 
Redordead89

Redordead89

Lovespeed:
Alright just checked out the boot Between the carb and the engine and noticed one of the screws was missing out on the boot. Could something small as that cause an air leak? It seemed to be sealed but maybe not. Also when I took the boot off I noticed liquid between the boot and plastic thing (idk what it's called) so maybe air was getting in through there?
Click to expand...
Is there any cracking or perishing at all on the boot?:noidea: ( the boot between the carb and cylinder)
Was the liquid oily? :noidea:
Replace the bolt and full top end gasket set if poss and go from there!:thumb:
You will get to see the condition of the piston, cylinder and rod bearings while you're in there:thumb:
 
L

Lovespeed

Redordead89:
Is there any cracking or perishing at all on the boot?:noidea: ( the boot between the carb and cylinder)
Was the liquid oily? :noidea:
Replace the bolt and full top end gasket set if poss and go from there!:thumb:
You will get to see the condition of the piston, cylinder and rod bearings while you're in there:thumb:
Click to expand...
The boot looks perfect, no cracks or anything. The liquid was oily feeling. Any cause to this? Here's a pic of it
 
Mihylo33

Mihylo33

Lovespeed:
Alright just checked out the boot Between the carb and the engine and noticed one of the screws was missing out on the boot. Could something small as that cause an air leak? It seemed to be sealed but maybe not. Also when I took the boot off I noticed liquid between the boot and plastic thing (idk what it's called) so maybe air was getting in through there?
Click to expand...



Yeah. A bolt missing out of the boot will cause an air leak. Is there a gasket for that boot where it bolts to the cylinder?

Edit: Just looked at the fiche.
There's a gasket between the cylinder and Reed block but the boot bolts directly to the Reed block.
 
Last edited:
L

Lovespeed

Mihylo33:
Yeah. A bolt missing out of the boot will cause an air leak. Is there a gasket for that boot where it bolts to the cylinder?

Edit: Just looked at the fiche.
There's a gasket between the cylinder and Reed block but the boot bolts directly to the Reed block.
Click to expand...
Is that how it's supposed to be? I've never had to deal with an air leak before so I'm not sure what to do. Should I just clean everything real good and stick it on? Should I get a new gasket for the cylinder/reed block? Also do I just stick the boot on or to I need to use some kind of sealant? I tried looking online but couldn't find any info about it that helps.
 
Mihylo33

Mihylo33

Lovespeed:
Is that how it's supposed to be? I've never had to deal with an air leak before so I'm not sure what to do. Should I just clean everything real good and stick it on? Should I get a new gasket for the cylinder/reed block? Also do I just stick the boot on or to I need to use some kind of sealant? I tried looking online but couldn't find any info about it that helps.
Click to expand...


Only replace the gasket if it's torn or mangled. No sealant needs to be on the boot at all.

My bet is the magneto side crank seal. With the cover off and the bike running spray some wd40 behind the magneto and see if the Rpms change. If it does. Replace that seal. However with an air leak this shouldn't be at max Rpms. More of a very high idle like a car with the choke still on.
 
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