Honda Twins banner
1 - 12 of 12 Posts

·
Registered
Joined
·
36 Posts
Discussion Starter · #1 ·
Recently after to much examination and try I found that booth carbs, no matter where do I move the plates advanced or retarder the carbs make explosions at low rpm 1500. what could be the cause?
 

·
Registered
Joined
·
608 Posts
some backfiring can be caused by timing or air leaks, are the carb intake manifolds in good shape? no cracks in the rubber, sealed to the carb and head correctly? low battery voltage will also cause the motor to run poorly resulting in backfiring and misfiring
 

·
Registered
Joined
·
36 Posts
Discussion Starter · #3 ·
I found that one had a small crack because of the explosions that generally when it's idlling they take off the carbs. and whe the carbs are taken of. I can see a fire came in from the rubber.
now I am going to see if I can found some rubber holder. I think that is going to be difficult. only if I found from another bike. The battery I think is ok, It's start with the electric motor and the battery it's new 3 weeks from purchase but, anyway I am going to give a small charge. I don't know if it is timming because if I move the plate counterclock almost to the top the right cilinder stops from working.
 

·
Registered
Joined
·
3,926 Posts
It's probably timing related. You NEED to check it now before you go any further. Verify that it's SPOT ON and then you can move to other ideas. Without verifying timing being the culprit, you'll never know if you've got anything else right or wrong!

GB :mrgreen:
 

·
Registered
Joined
·
36 Posts
Discussion Starter · #5 ·
the timming apparently when is ok is where it makes more explosions.
I am getting out of ideas so I think that can it be to high the level of the carbs. the only thing that could be as I publish in my last post could be that the crancase would be a teeth more but acording to the marks are really near.
 

·
Sensei
Joined
·
27,183 Posts
Near is NOT acceptable... Crankshaft/camshaft timing MUST be EXACT.... ONCE SET, LEAVE IT ALONE!

Then do points timing, static and then strobed at idle and full advance...Again, once set and right, leave it alone!

Then carbs......

If you keep changing more than one setting (thing) at a time, we will never be sure what is wrong or how to fix it....

And, I never heard results from a compression check....
 

·
Registered
Joined
·
36 Posts
Discussion Starter · #7 ·
sorry because in order to take the compresion I have to ask to a friend if he let me the device to check it. but I have to admit my pistons are not the original ones. are from a cbx200. they are almost identical. I have the originals but one of them had a little tear because of a valvle.
the timming plates are in their marks and the avance mechanism works just fine. but in that position the left carb makes a lot of explosions. the right one some times. I only move the timming plate in order to try to avoid the explosions but whitout succses

I'm from uruguay (south america), the country between argentina and brazil. let say at least 10 years learning english to take the cambridge cpe, but I couldn't pass it yet.
 

Attachments

·
Premium Member
Joined
·
2,154 Posts
alexis159
Valve clearance too tight on left cylinder?
BTW, where are you?
you English is way better than my Russian/Croatian/Swahili/etc
PJ
 

·
Sensei
Joined
·
27,183 Posts
Did you fix (replace) the valve that caused the "tear" in the piston?......
With what? (a 350 valve or a CBX200 valve?)....New valve guide?....
How close ARE the "new" pistons?.....(same "dome"..same pin to crown height?)
Did you "fix" the head?.......Was a connecting rod damaged?

A tight, bent or improperly seated valve could cause those problems.....
This is one reason why we need a compression check.......

It is just as frustrating for us to give advice that is not followed as it is for you to have a bike that does not run correctly.... Even more so, because you did not give us ALL the necessary information at the beginning......We are trying to help, but need all the pertainent information......Otherwise, we assume the engine and its parts are stock or correct for that model bike........
AND, They ARE NOT!....
 

·
Registered
Joined
·
36 Posts
Discussion Starter · #10 ·
sorry about that little detail, and about the valvle is an original cb350 I bought form ebay. I send the head to a company to fix the problem new guides and fix the valvle seat. for now I check with my finger and have aparentlly a good compresion same in booth sides.
But the worst thing is that some time ago(6 months) with this pistons and all the bike works normally but when the advance mechanism was broken the problem just began. problems in carbs, diapragms. now The funny thing is last week I could use it without any problem only that only was reaching 6000 and more or less 67mph I remember that before I had reach more or less 94 mph. Bytheway I don't know why when the bike is near 6000 rpm sound like if it was like 10000.
 

·
Sensei
Joined
·
27,183 Posts
Don't run the engine unless you want to start a fire or blow it up..... And don't expect any further response from me until you run a real compression check, re-set the valve clearances, check and properly set the crank/cam timing, set the points timing to specs, and reset the carbs..... You won't have to worry about the camchain being "off a tooth" if you first fix it to factory timing specs...... EXACTLY ON THE INDEXES!..... Same for the points timing, etc..... Until then, I'm done....

Dude!..Why ask for help and then not accept it?.....
 

·
Registered
Joined
·
36 Posts
Discussion Starter · #12 ·
I just check the compresion in cold and its says 7. so I think that should I start looking for a new piston with 0.50 but It's a little hard to find in this measure. and I only need one.
bytheway I have a a vaccum a tester for carbs. the same as a sincro carb but do I have to make a hole in the rubber that conect the carbs from the cilinder.
 

Attachments

1 - 12 of 12 Posts
Top