Dial indicators

[Andreas Piepke]

Hi All,

I want to buy a dial indicator to set my ignition timing properly. I've found two reasonably priced devices on ebay (both come with a spark plug adapter):

http://www.ebay.com/itm/PVL-IGNITION-TDC-TIMING-DIAL-INDICATOR-SHIFTER-KART-SPARK-PLUG-THREAD-NEW-/161467728292?pt=Motors_ATV_Parts_Accessories&hash=item25983a01a4

http://www.ebay.com/itm/PVL-IGNITION-TDC-TIMING-DIAL-INDICATOR-SHIFTER-KART-SPARK-PLUG-THREAD-AIR-COOLED-/151458524624?pt=Motors_ATV_Parts_Accessories&hash=item2343a1add0

Can anybody advise me whether the short unit (first link) would work or one needs a device with extender (second link) to clear the cooling fins. In the latter case clearing the frame is a concern. Any insight would be appreciated, I don't want to buy the wrong thing!

Thanks

Andreas

[454MRW]

The first one looks promising, but probably not long enough threaded section to allow clearance to the head, and the last one poses a problem with the top piece extending upward,  which would interfere with the frame backbone on some bikes like the MC5's especially if you are using it on an installed engine. You can always extend the measuring tip with a piece of stiff tubing. I use clear gas line. Check out this thread on dial indicators:
http://pentonusa.org/forum/topic.asp?TOPIC_ID=15636&SearchTerms=electronic

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[thrownchain]

Check out ebay # 151336186288. It has all the spark plug adapters and extensions. I bought this same set 30+ years ago and it still works like a charm.

[wfopete]

Andreas,

Be warned. A few weeks ago I bought the very same 2" travel unit (from the same vendor) as you show. When I got it the unit was jammed up and would not move except by force.  To be fair the seller promptly returned my $ as soon as I returned the unit.

So today's lesson is: Don't cheap out equipment when you need quality.




Pete Petrick
175 Jackpiner
Slow but Good

[Kip Kern]

I used a old sparkplug cut off and welded a pipe nipple on it for the long reach.  Brown and sharpe dial with extenders and works great for the modern 4 strokes.  For the old bikes, I use the Sachs timing tool.  The latter is easier than the first

[derek martin]

I bought the Motion Pro timing indicator several years ago - works great. The long adapter is needed for air cooled bikes. The indicator kit and adapter are shown on their website.

[Andreas Piepke]

Here is what I got. A used Mitutoyo 2050-01 dial indicator ($20 plus shipping on Ebay). Moves smoothly, I confirmed the overall correctness of its readings against a depth gauge with 0.01 mm resolution. I further bought an adapter (another $20 plus shipping on Ebay, from Hungary) that mates the spark plug hole. Both items are shown on the image below:



The adapter had to be modified. It had an 8 mm inner opening, while the Mitutoyo instrument has a 3/8" stem. The adapter was further shortened a little and a step machined into it as I only have a 3/4" tip which is a bit too short. After that both components fit nicely:



With a little twisting of my fingers I can install this into the cylinder head, there isn't much clearance. The piston touches the gauge and I can measure its position:



Now comes the issue: the engine is rebuild and has good compression, I cannot control the piston position enough to stop its motion at TDC. How do I find TDC and then back off to the desired distance? I tried putting the engine in gear and rotating the rear wheel for more control which doesn't work either.
I have a manual from Al Buehner. It has a white part (for older models I guess) and a yellow part (for newer models). The white parts states an ignition set point of 2.55 mm btdc while the yellow pages give 2.25 mm btdc. Interestingly they use the German acronym for this "V.OT" meaning "vor oberem Totpunkt" or "before top dead point". Would anybody know the recommended value for a 1973 (model year 1974) Hare Scrambler?

Cheers and thanks in advance!

Andreas

[454MRW]

Grasp the flywheel with your hand and rotate the flywheel back and forth by hand and you should be able to find top dead center as you watch the dial slowly stop changing then going in the opposite direction. Set your dial at 0 at the center of the movement and that is top dead center. You can go until it reads 5mm in each direction and make a mark on the flywheel and 2 on the cases then measure to the center between them and make a top dead center mark on the case for future reference. Then once you verify the center point and reset the dial at 0, turn the flywheel counterclockwise until the dial reads -2.25 to -2.55 depending on what setting is recommended by the group. The 74 instruction manual recommends 3.0 before top dead center, so there is varying information. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[wfopete]

The trick for me is holding the crank assembly in place while tightening the flywheel nut.



Pete Petrick
175 Jackpiner
Slow but Good

[skiracer]

Pete, your timing should be set before you need to tighten the flywheel nut.  As long as the key is on the shaft, the flywheel can't rotate by itself.  Make sense?

quote:Originally posted by wfopete

The trick for me is holding the crank assembly in place while tightening the flywheel nut.



Pete Petrick
175 Jackpiner
Slow but Good

1976 MC 5 Original Owner
1982 Suzuki PE 175
1976 Penton 175 GS
1976 Penton 250 GS

[Andreas Piepke]

Thanks for the feedback! The issue of an extremely sudden and hard to read response of the dial indicator had an interesting cause. The assembly was almost gas tight so what I saw was the compressed gas just flicking the plunger. I drilled two small holes into the dial indicator holder to vent the gas when the piston approaches TDC. This actually revealed that the tip of the dial doesn't even touch the piston. Now I can smoothly rotate the crank without having to fight the compression.
The advise regarding how to get the right setting are useful nonetheless. However, it does seem hard to gauge where the key points at the stator and how to rotate it. One can't see anything with the flywheel in place.
I just ordered a longer dial indicator tip from McMaster-Carr. The job, unfortunately, needs to be delayed until I get the parts. I guess I will have to find out what the correct ignition setting for my engine is. I would hate to burn a hole into my brand new piston. Maybe I'll make another post.

Thanks for you input!

Andreas

[454MRW]

You do not need to see anything behind the flywheel to set the timing once top dead center is determined and marked on the outside of the flywheel and a corresponding mark on the case above the flywheel mark, and resetting the gauge to 0. With the Motoplat just slight loose, insert a slightly snug fitting drill bit or timing tool into the hole in the flywheel and engage it in the corresponding hole on the Motoplat its self then rotate both the flywheel and Motoplat together to the desired setting, then remove the tool and flywheel and tighten down the Motoplat screws and you are done except for re-installing the flywheel and tightening down the nut. I mentioned the setting of 3mm BTDC in my previous post because I thought you were referring to a Jackpiner, but after reviewing your post I realized you are asking about a 250 Harescrambler, which is listed as 2.55mm BTDC in the 74 Instruction manual. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[Andreas Piepke]

Hi Mike and all others,

Thanks for the procedure and the set point data. That's what I will do then!

Andreas