A forum for owners of Yamaha TTR250 trail and enduro bikes!

Members Login
Username 
 
Password 
    Remember Me  
The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> Starting problems
Post Info TOPIC: Starting problems
Wee Jessie


Newbie

Status: Offline
Posts: 2
Date:
Starting problems
Permalink  
 

I've just finished checking the cylinder head of my TTR after a worry some grit got in when I removed the spark plug. There was a bit of fine grit/sand on the crown of the piston but the valves 'seemed' to be clean and were seating ok.

After the rebuild, the bike initially started but stopped after a couple of seconds. Further attempts to start have been unsuccessful, with the odd backfire thrown in. I'm getting a good spark at the plug but it looks pretty dry, even after several starting attempts.

I'm starting to think there may be a problem with one of the valves not seating properly. Any thoughts???confuse



__________________
Cubber


Super Guru

Status: Offline
Posts: 2610
Date:
Permalink  
 

If it was running OK before you removed the plug to drop grit in then it may be fuel supply problems - because you would have removed the carb to get the head off!
Did you return all the dismantled bits back into the head? Correctly?
Check to see that you have fuel in the float bowl before any further dismantling to check your valves.

An engine needs two basic elements to run - petrol and spark.
Preferably these require putting in to the cycle in correct quantities.
Lack of either can cause problems.

Check each, in turn, one at a time. This method will save you curing the defect and not knowing which was the cause.

Fuel check - tap, pipe, float, float needle, float level, jets, air valves.

Spark checked OK so shouldn't bee the culprit but look at the plug, plug cap, lead and connection to coil.

Check for cylinder compression then check that valves are opening in correct sequence and with correct clearance.

If nothing comes to light then you've got other things to worry about and probably need to ask here and give more info.
Good luck.

__________________

You're never too old to learn something stupid

East Budleigh. Devon
TTRfan


Super Guru

Status: Offline
Posts: 8606
Date:
Permalink  
 

Cubber's advice is good. The symptons suggest a fuel problem.

The worst case scenario is that the valve timing was out and that the piston clobbered and bent a valve. Easily checked. Have you got compression? If a valve has been bent there will be none.

If an inlet valve is bent then mixture will still be drawn into the combustion chamber but would backfire out the inlet tract. Don't ask how I know cry

Some useful tips in the "how to" here http://www.ttr250.com/Removing_Cylinder_Head/TTR_head_removal.htm

Brian



__________________

Exeter, Devon, UK

http://www.ttr250.com  - The one and only dedicated TTR250 FAQ!  

TIP: For easy viewing bookmark the "Recent Posts" view - http://ttr250.activeboard.com/p/recent/ 
Wee Jessie


Newbie

Status: Offline
Posts: 2
Date:
Permalink  
 

Many thanks guys. There is compression and I couldn't see anything obviously wrong with the valves, so maybe it is the fueul supply.

This is all very helpful advice and sets me up nicely for the weekend!!

Cheers and thanks again.

__________________
TTRfan


Super Guru

Status: Offline
Posts: 8606
Date:
Permalink  
 

A quick and easy way to check if its fuel is to spray something like EasyStart (ether based I think) into the inlet - that should wake it up if it is a fuelling issue wink



__________________

Exeter, Devon, UK

http://www.ttr250.com  - The one and only dedicated TTR250 FAQ!  

TIP: For easy viewing bookmark the "Recent Posts" view - http://ttr250.activeboard.com/p/recent/ 
Page 1 of 1  sorted by
 
Quick Reply

Please log in to post quick replies.
The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> Starting problems


Create your own FREE Forum
Report Abuse 		Powered by ActiveBoard