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1600/1750 weak start motor ?

3K views 23 replies 5 participants last post by  alfatrym 
#1 ·
I put a 1750 motor in my Duetto , using the old transmission/bellhausing /flywheel /startmotor (2-bolt type). I have started the car many times now , and it runs fine. But the starter has allways cranked the engine over very slow . Almost stopping up sometimes. Even before droping it in the car. I've had the starter apart , and done all the tests I can find on you tube, using a multimeter, but I can't find anything wrong. Bearings/bushes ,teeth ,brushes look good. no internal rubbing. The battery is New and so are all the Heavy cables (I have not done voltage drop test over these -I will ). Maybe the brushes could be dressed better (there are only 2) ? Is this motor to weak for the 1750 ? I have never had the 1600 running - so can't compair - but I don't realy think the larger engine is the problem.
Any advice to get here ? Thanks !
 
#3 ·
Jay is right !
Check the timing.
If the starter doesn't turn very quickly or it makes troubling noises, you may have the wrong tooth combo on starter/ flywheel.
Or the starter may need a rebuild, or the engine has too high compression.
 
#5 ·
The combo - starter /flywheel are from the original sett up -they have always been together. .I can buy a New starter - it would have to be a Three bolt -thats all I can get New. But The original starter is pretty simple - everything looks good - and I would like to find the cause first.
 
#4 · (Edited)
I set it at the F mark or was it T , - the one right next to P. To much advance and it has a very hard time. But even doing a compression test , it slows Down alot on the compression stroke. I should also mention that I have a groud cable to the engine (+ an exstra one to be sure), and I had no voltage drop over the solinoid. The comunicator on the starter was kind of dirty. I cleaned it up but dident do much With the brushes. Think I should try filing them flat ?
 
#7 ·
Yes ! So I take it that- these old starters normaly don't have any problem cranking the engine at a good speed ? Concerning the 1750 , I bought it a long time ago . no starter or alternator. Though I havnen't opened it up , Everything about it ,tells me that it hasen't been modified, or worked on. I'll try and dress the brushes a little better , maybe get some New ones if posible. In the end -if it dosen't work - I'll give up and buy a New.
 
#11 · (Edited)
I'll try and dress the brushes a little better , maybe get some New ones if posible. .
There may be some benefit in having a professional electrical shop test and possibly rebuild the starter. They may find that there is a broken/shorted lead in the armature or field, or some other problem that isn't visibly obvious.
 
#8 ·
When new, there was no problem with the standard parts !
On such an old car, don't assume anything.
Once, my '64 Spider blew a head gasket. Fixed everything including having the radiator rebuilt to get the oily milkshake cleaned up.
After reassembly, the car would over heat quickly just at idle...
Checked all of the usual suspects, all good. /then pulled the shinny newly rebuilt radiator and took it to another shop to test..
75% clogged.....
All the first shop did was to spray it black.
 
#10 ·
I hear You. The New starter is for a 1750(3 bolt) With 110 tooth starter ring , but it will also work on the old style 2 bolt belhausing With 105 teeth, they claim. Proably true , but there have been some disapointments With New parts. Papajam has had some posts about this topic and i Guess they did switch to a different style starter (3 bolt) in 1969, wich was a replacment for the old 2 bolt style starter. But that was when Alfa was running the show.
 
#13 · (Edited)
Remove the starter solenoid and reverse the "Shorting bar" on the end of the shaft. This provides better continuity where the bar touches the contacts and more current is available to turn the starter motor. I did this on a 1971 1750 spider, and the increase in cranking speed was significant.

Edit: I just realized you said there was no voltage drop over the solenoid, so my advice may have been in vain...
 
#14 ·
I think I have found the problem . On the second check with the Fluke , I found the field coil is leaking to ground- 35 m ohms.
I was not albe to loosen the 4 big screws holding it , but gave the screws some penetrating oil and I'll try the impact driver tomorrow. A new field coil is located , and is about half the price of the new starter . I'll get it of ,and take a look at the problem first , but I am tempted to try and fix it with a new FC.
 
#17 ·
I have taken the starter apart, So it's just the Field coil bolted to the barrel/house. Lead inn from the solinoid - lead out to one brush. Some where along the path there is a leak to ground. I'll try to find it later to day if I can get screws loose that hold the Field coil. All the info I can find says to replace - don't try and fix bad isolation.
 
#20 ·
Does a new starter need break-in time ?I caved and bought a new starter. BUT it dosent sound very nice very nice cranking - almost like starter gear spinning to fast before it engages . it has the correct -8 tooth gear and same size an shape.the posisjon/ moment on the bendix appear to be the same , as the old one. Only real differens I see is the teeth on the old starter have more slant cut on the gear ( the side that engages to the ring gear. time done this? ) .Hmmmmm. This new one almost dosent have that cut (yet). other that that it has no problem spinning the motor around. worried about chewing up the ring gear. Does it need a little break in time ? or will it break everything. ?
 
#23 · (Edited)
No , this is 1750 conversion . I use the old gearbox /flywheel and the old shim (5-6 mm- 1/4") thick. 2 holes , no spesial bolts.The shim you are taking about has 3 holes ,and is for use with the later gearbox /fly wheel - it won't fit here. The old starter has 2 bolts , the new one has three - one is not in use.
 
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