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Ollie cams and ignition timing

Moderators: Curt!, Pa

Post Fri Aug 24, 2007 11:17 pm

Posts: 41
Location: Lakewood, Washington USA
I just rebuilt a 1946 Chief using Ollie cams, stock ignition timing, a M88 carb with Bonne throat and jet. Today it started for the first time: two priming kicks and away she went! I was a bit surprised at how easily she started the first time around. The only thing I noticed was that she popped out the exhaust quite often at idle at anything less than fully advanced: not a backfire per se but rather early exhaust opening with timing that's too late (even if stock) I suspect. Mixture looks OK from plugs and the headers did not discolor so I think I'm still within limits. I can understand the popping given the high lift/duration cam. I'm wondering though whether the ignition timing should be a bit more advanced than stock to give a smoother idle and running. Even fully advanced she did not kick back when I started it. My '39 Chief ('48 engine) with stock cams and ignition timing runs like a clock but has to have the timing retarded to start or it will break you leg.

John A

Post Sat Sep 01, 2007 11:37 am

Posts: 124
Location: Glenmoore, Pa. USA

One must first know if the Ollies are old originals or late model reproductions? Are they pinned on old gears? How are we sure of their timing marks? Were the cams set with a dial indicator for opening and closing in relationship to cylinders or were "Timing marks" Used?All timing needs to be done from rear cylinder as per the factory racing school. When rear cylinder is 5/8 inch to 3/4 inch before TDC, magneto or distributor should be fully advanced with points just opening on wide lobe.
Could you have some Taiwan repops for cams? Where did the cams come from?

Post Tue Sep 25, 2007 11:20 am

Posts: 2
Hello there.
I have just joined up today. I have a 1937 74" Chief with magneto. At the moment it is undergoing an engine rebuild and I was wondering,having read this post about timing, whether I can assemble and time the magneto on the bench and still manage to fit the whole lump in the frame easily. I only ask this because it is obviously much easier to work on it out of the bike.
I have to time the magneto again as I have lost the timing mark on the gear. The shaft was replaced a few years ago and was never drilled and keyed as suggested in the manual.
Does anyone yet/still supply Bonneville lifters to go with Bonneville cams or even Bonneville cams for that matter? Are Ollie cams useable with the standard lifters and are they just a shrink fit on the gear shaft?

Yours Chris Geddes in England

Post Tue Sep 25, 2007 12:45 pm

Posts: 202
Location: Middle England UK
Is this a "pop" or more of an iregular "pom"?
If so try opening plug gaps a couple of thou.
I've had this on cars,trucks and bikes that just don't like the factory settings.Don't know why or how but it worked,fine by me. :D

Post Wed Sep 26, 2007 6:00 am

Posts: 39
Location: Paris, France

Pakyan wrote:
Does anyone yet/still supply Bonneville lifters to go with Bonneville cams or even Bonneville cams for that matter? Are Ollie cams useable with the standard lifters and are they just a shrink fit on the gear shaft?

Hi Chris,

Ollie cams can run with std followers, that's what I use. I've heard they perform better with Bonneville followers.
Bonneville cams need the Bonneville followers
Bonneville cams and followers are listed on Kiwi catalog : ... t/92908|9/ ... /41848|50/


Post Thu Sep 27, 2007 1:31 pm

Posts: 2
Salut Fred.
Quel surprise de te trouver ici! Je fais des progrès sur la machine enfin. Faute de poignon n'est ce pas !

Salutations Chris G

Post Thu Sep 27, 2007 4:26 pm

Posts: 41
Location: Lakewood, Washington USA
The Ollie cams were obtained from Jerry Greer and are pinned to original timing gears and alligned with the original timing marks. Ignition timing was set statically on the $ using the front cylinder and then checked dyamically with a timing light.....right on.

At first I thought popping out the exhaust was an ignition timing issue and discovered that there was quite a bit of play between the distributor shaft and oil pump return drive shaft. I took care of that with a small brazed bead on the distributor shaft end which was filed to fit and now there is very little play and ignition timing dead on....and stays that way. That helped. Although the plugs looked good (although a bit rich) after running at speed (30-40 mph for break in) I discovered the stock plugs sooted up badly at idle and that perhaps running very rich at idle was part of the popping problem at idle. I went to hotter plugs and that also helped. I've heard that back in the day, using hotter plugs to break the engine in was common place. The engine does not backfire at speed (unless to close the throttle quickly) and in fact the performance at open throttle is pretty amazing compared to my stock '39 Chief. Leaning the idle down brought its own issues such as starvation when the throttle is opened up: there isn't much room for a transition between idle and high speed needles. I'm using a M88 carb, internally vented with a slotted 1 1/8" venturi and Bonne nozzle. It may just be that this engine is going to need some time to break in before it's ready to set up. I don't know that the rings have seated yet after about 50 miles and that may be part of the problem. The more miles I've put on the bike the less of a problem the popping has become and it has a relatively smooth idle.

Will let you know how things turn out. In any event, the Ollie cams have given my '46 Chief a serious performance kick in the pants and I would consider the same modification in my '39 when rebuild time comes around.

Post Thu Nov 01, 2007 7:53 pm

Posts: 41
Location: Lakewood, Washington USA
Well I finally found the problem with my M88, Bonneville venturi and nozzle, Ollie cam'ed '46 Chief engine: it was the nozzle. The engine ran rich at idle, came off choke very quickly, the low speed needle was unscrewed about 10-12 clicks out from a good idle, there was backfiring, starvation when opening the throttle, but ran well at speed. I played with ignition timing, float levels, mixtures, hotter plugs, etc. but didn't quite seem to get it running right. Turns out the Bonneville nozzle holes (.052") were letting in too much air too early when the throttle was initially opened thus leaning the mixture and starving the engine in transition. I went to a modified stock Chief nozzle (.043" holes and larger ID to increase flow). That may not appear as much of a difference but the results were immediate. First thing, the low speed needle went in 12 clicks were it belongs. Previously it had to be set too rich to compensate for the lean mixture in transition. Response was very smooth and seamless from idle through transition to speed: no stumble, hesitation, black smoke and any sign of backfire. An amazing difference! I pulled the plugs after a short ride and they looked almost new! I will probably go back to the cooler stock plugs since I don't have to worry about carbon fouling any more.

I'm not sure why the Bonne nozzle didn't work with the Bonne 1 1/8th venturi but it may have something to do with the design of the M88 Linkert . The original M88 used a main jet (now plugged), a 15/16th venturi and nozzle with only 4 holes instead of 5 like Indian, and they are very small (.038") and set lower on the nozzle. Clearly the M88 ran a much richer mixture in the nozzle. In any case, my experience with the M88 shows that while not a direct swap it can be used successfully with a souped up engine if you pay attention to the nozzle and transition problems. I want to thank Victory Library for their Linkert book which helped me diagnosed the problem......and probably saved me a bunch of money to unnecessarily replace the M88 carb when only the nozzle needed attention.


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