Tried this earlier, don't see my post??
My 73 has the stock original 1700 engine, serial CB083892, which tune up specs say is 10 ATDC at idle of 950rpm. Before starting I checked everything and was surprised that it was running at 27 BTDC!
When set to 10 ATDC or even the default 7 BTDC it backfires and refuses to start when it is hot. I returned it to 27BTDC and it is ok.
Anyone have experience with this problem? I can't be sure the timing is set even close to optimum under the circumstances.
Things that may be important: the distributor is centrifigal, no vaccuum advance, the fuel pump must have failed and it has an electrical fuel pump on the wall behind the dual carb, wires are going to correct plugs. Also this bus maint record shows it was purchased in Germany in 73 and brought here (probably by one of our military families) in 74. It has the German wide bed under the tent instead of the fold over cot but side lighting, sealed beams, etc are DOT spec for 73.
I noticed that the 73 1700 model EA and EB(calif) are set to 28 BTDC at 3500rpm, which is curious, but mine is 27 at idle and it runs. What might I have to do to correct this?
Timing of 73 Westy
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raygreenwood
- Posts: 11907
- Joined: Wed Jan 22, 2003 12:01 am
The 1.7L were factory timed at 27BTDC...on most fuel injected models (not sure about carbs) at 3500 rpm to make sure that the timing was all in at the main rpm level. This settled out ot about 8-10 BTDC of idle timing.
My bet is that you do not really have 27BTDC in real world timing.
Question: what marks or notches are installed on the pulley? If it is a 1.7 and the engine is original for those years...it should have a "0" or black marked stamped at TDC and a red mark or black mark about 2" to the right of that for 27 degrees. If it has only one mark....it may be a later fan or one of the variants from a 914 or 412 1.8.
Its also possible that the fan has been off the hub and that it is not exactly back on the dowel or the locating dowel is missing....though that would usually get you a lot farther off than 27 degrees.
Also....on the bus.....the timing mark is read from the front looking into the fan at a scale that is offset to the left side of the engine. The timing scale could be incorrectly installed or bent.
The bus fan had different marks to be able to use this scale.
Where are the marks on your fan pulley and what scale are you reading against?
My bet is that you do not really have 27BTDC in real world timing.
Question: what marks or notches are installed on the pulley? If it is a 1.7 and the engine is original for those years...it should have a "0" or black marked stamped at TDC and a red mark or black mark about 2" to the right of that for 27 degrees. If it has only one mark....it may be a later fan or one of the variants from a 914 or 412 1.8.
Its also possible that the fan has been off the hub and that it is not exactly back on the dowel or the locating dowel is missing....though that would usually get you a lot farther off than 27 degrees.
Also....on the bus.....the timing mark is read from the front looking into the fan at a scale that is offset to the left side of the engine. The timing scale could be incorrectly installed or bent.
The bus fan had different marks to be able to use this scale.
Where are the marks on your fan pulley and what scale are you reading against?
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wildthings
- Posts: 1171
- Joined: Thu Jun 03, 2004 12:42 am
The 10° ATDC timing is for a dual vacuum dizzy with a working retard function. If you do not have any vacuum can then this spec does not apply to you. You probably have an 009 distributor. The centrifugal advance curve of an 009 is typically not well suited to a heavy bus and tends to give poor performance at lower rpms and slightly worse gas mileage at any speed. The bus timing specs were typically 28-32° BTDC at full advance ~3500rpms.
As Ray mentioned you must have the correct bus timing scale and a correctly marked pulley. Without either you will not get your timing on spec.
As Ray mentioned you must have the correct bus timing scale and a correctly marked pulley. Without either you will not get your timing on spec.