Vintage Dirt Bike Q & A

Hi folks,
Just completely rebuilt CR125 Elsinore 1976.......however, I have a problem with low revs! the bike starts first kick, idles super but seems to struggle to get the revs up (bogging?) once the revs reach @ 2000rpm or so.........it's off like a rocket, just doesn't seem to want to rev cleanly and I've also noticed there seems to be excessive oil coming from the exhaust at the cylinder........ Any suggestions welcome

Cheers people
Malcolm

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1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!

Malcolm,

Does it start first kick when cold without the choke? If so, could be the pilot circuit's too rich.

My '74 idled fine and had a similar hesitation off idle - turned out to be mainly a leaky LH crank seal, along with a too-big carb and porting issues.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

thanks Ray for the info,

no........the bike wont start when cold without choke!! and the engine has been completey stripped and rebuilt with all new parts so I would doubt leaking at the crankshaft seals and besides has really good compression. I think it's definenately a carb problem but I suppose it's a matter of trial and error! I have replaced the carb with a nearly new 33mm Keihin although the standard is a 30mm Keihin of which I have 2 more alll with different set-ups the one on now seems to be the best I'll just after keep on tinkering

Cheers Ray
Malcolm

p.s. here's a little pic of the bike I'm going to road register it soon hope ya like it!!

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1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!

Malcolm,

The bike looks sharp! How do you power the lights, a battery?

Re the carb... I'd just keep plugging away at the air screw and pilot jet if the hesitation is around 1/8 - 1/4 throttle, and the slide and/or needle straight diameter if it's closer to 1/4 - 1/2 throttle. Your carb looks like a newer one, should be parts available for it.

My CR used to chuff mixture back out the carb throat at idle and low rpm; I never noticed it until one time I started it without the air boot. It's worse with the -810 suffix Honda piston, or if the intake port's been modified (mine had both), and the 36mm carb didn't help either.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Thats what we used to call loading up. You can put the throttle wfo but it wont take it, but if you S L O W L Y reduce throttle to almost 1/4 it will take off. Typical of piston port engines.
They load up the crankcase with unburned fuel, once they clean out there ok for a while. Problem is too much fuel and not enough revs. Jetting usually isnt the problem.
Now you see why reed valves were invented.

I used to see many an elsinore sitting at the side of the track with the low rpm grumbles. Like I said, hold it wfo while it grumbles, then slowly reduce throttle and I mean slowly, it wil take off and be ok for a while till it overfuels the bottom end. Also reason why you see wet at the exhaust flange.

Good luck.

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1994 AHRMA National Champion Sportsman 125 Intermediate.
1996 AHRMA National Champion Classic 125 Expert.

Hello Ray and the other Chap,

thought about modifying to a reed system but I think it would be a lot of machining involved not to say that i might have ago at it with an old cylinder sometime I'm just trying to get a happy comprimise.

the lighting is a German system I had made, its absolutely great no machining to do, simply replace old with the new one and fit the distance spacer between engine and crankcase cover (see pics) the system delivers around 120 watts more than enough for head and taillight, horn and a couple of indicators, wiring it all up is around a 2 hour job when you have everything at hand.

what is the term wfo? cant figure that out!!!

cheers anyway
Malcolm

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1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!

Malcolm,

Wow, that's some serious ignition system you've got there. Honda really should've put ignitions like that on the MT and MR bikes (like Suzuki had done years earlier with their TS series) which would have made adding lights to the CR's much easier. Can the German place produce more, or was this a one-off?

The reed valve suggestion is an excellent one. If I ever get around to resurrecting my original CR motor, that's the route I'm going to take.

I believe Honda kept increasing CR125M intake port duration to try and keep up with the reed motors at least in peak power, but that makes piston-port motors run crappy down low. If you lean out the jetting to compensate, you lose your throttle response at higher revs. The MR175 (and MT125) have very different intake timing/duration, and pull cleanly under load from below idle if jetted even close to correct.

WFO means "Wide F-ing Open".

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Hello Ray
the igniton system is now developed, I believe this system could be made for any bike really, Cr's, Rm's, Kx's, Yz's and just about anyother.
If you've noticed on the pic it's changed from an internal rotor to an external if you get my drift.
I have them on my yammy TY's all the range from an 80 through 250
I can order as many as you want. The distance spacer I make (or rather programed on a laser cutter)

I forgot to add:- the system is from circa 200 to 18,000 rpm with a smoothing condensor to limit overcharge, basically it's a full kit:-
new stator
new rotor
new coil + H.T. lead
smoothing condensor
rotor tool (for removal)
and instuction leaflet
all fits very neatly under the tank on the original mounting lugs no drilling needed. everything runs off the system (of course only when the engine running) no battery required
hope thats enough info for ya let me know if your interested! I could give the chap a call
the only problem I can see is the price per unit, I reckon around 450dollors + postage.........possibly cheaper for maybe 5 units
all depends how serious someone is I suppose

cheers Ray
Malcolm

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1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!

Malcolm,

Thanks for the photo and info. That looks like a really nice ignition. I wouldn't mind getting one myself, and a friend of mine may be looking to add lights to his bike so I'll ask him about it too. I assume there are marks on the rotor for setting the timing? Can the maker supply info about the advance curves in the CDI unit?

The MT125 / MR175 ignition covers are wider than the CR ones to fit the stock flywheels, so that might be an option for this setup. My MR is using the stock cover with a CR125 ignition, and there's a lot of room in there.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Just get a GEM or DH reed valve, they just bollt on;

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1994 AHRMA National Champion Sportsman 125 Intermediate.
1996 AHRMA National Champion Classic 125 Expert.

That is one awsome resto job on the cr125. I've got one that looks almost exactly like it that I'm waiting for a few more parts to finish it up. I've tried to post pic's of it but for some reason can't get them to post. I'll keep trying. Is there any way I could get you to take close up shots of the foot pegs and carbeurator drain hoses, I don't know how to install the foot peg springs I ordered, they just don't seem to have any room left to attach them on the securing pin. The carb. overflow hoses are another question. I have a Minki 34mm round slide and don't know exactly how the hoses were routed. Can't seem to get a clear pic of any on the bikes I've seen online. Maybe another pic of the side number panel's, a close up of under the bottom of one to see how they secure to the frame would be nice too. I made my own securing straps for mine and want to make sure I've got them as close to correct as possible. Thanks, I know I'm asking alot but your bike looks awsome and I'd like mine to look about the same when completed next week. I'll also post pics to this listing so you can see the results, you'll be amazed how close these bikes look alike.Thanks for the pic's you've already posted and I look forward to the one's i've requested
Kenny
CR125M
Proud owner

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Kenny Rogers

'76 CR125M Elsinore

Hello Kenny,

here's a couple of pics!!.............but why do you want the springs anyway? I don't have them on mine....just nip up the bolts with safety nut and leave them a little free play they drop down anyway, the springs tend to get full of crap and scratch the paint off!! but your choice

Cheers Malcolm

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1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!

The main spring section slides over the straight-rod part of the inner peg end, the large end hook goes over the main footrest support, and the smaller hook clips over the rear footpeg support on the frame. The pic below shows the spring mounted on the peg:

http://straightupcycleparts.com/img/107 ... _02_xl.jpg


On my bike the left upper carb vent hose is really short and runs straight down towards the motor, the left bottom hose runs first through the hose clip on the rearmost case screw (near the swingarm) and then down through the hole in the case rib, and the remaining hose also runs through the clip and then behind the motor and down.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Long time!
finally got round to my problem!! put back original ignition, went down to a 28mm carb standard settings..........low and behold like brand new the bike is absolutely spot on.
My problem is however not finished, I have to fathom out why my new system isn't working as it should
I think it is almost definenatly the set up on the new system (Advance-retard) the stator and rotar have markings on them but the position of the stator on the crank is critical and that has no markings as to the position it should be mounted (bollox)!!! instructions with the ignition are a vague (igniton coils set at twelve O'clock) and then simply match the markings bolt up and off you go. (not so simple)
well heres to fiddeling
Malcolm

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1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!

If it were me I would put the OEM ignition back on as a reality check. It may run super well.

Does the aftermarket ignition have a TDC mark? At least you could get it within ballpark-correct timing that way.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric