What performance should I expect from my 1974 1000c

M

Mtoliva

Junior member
Location
London
I’m running a 1974 pre oil cooler 1000C with stock cams and new omega pistons. It has a DMC 32 from a previous rebuild. The engine just finished a total rebuild by Ged and Keith, so as good as new or maybe even better due to their amazing knowledge and talent.

My question is what sort preformance should I get from a 50 year old bike like this. She runs beautifully, but find that she won’t pull away from standstill at anything less than 3000rpm and takes off best at near 4000rpm. She cruises nicely at above 4000rpm. In 5th I get 60
Mph at 4000 and 70mph at about 5000rpm. I haven’t tried to find her top speed, nor do I plan to, but give the above, I’d be surprised if it were much above 100.

I’m not after more performance, I like the old bird the way she is, but I would like any comparison with similar early 1000’s
 
Well, it should break the speed limit easily. But are you sure your cams and carb settings are stock? The original cams are quite tame and it should pull away from tickover. Or you have ame kind of race gearbox :)
 
Mtoliva said:
She runs beautifully, but find that she won’t pull away from standstill at anything less than 3000rpm and takes off best at near 4000rpm. She cruises nicely at above 4000rpm. In 5th I get 60
Mph at 4000 and 70mph at about 5000rpm.
Click to expand...
Something does not appear right. You should be able to pull away cleanly from around 2,000-2,500 rpm and hold in gear, on a very light throttle, from 1,500-2,000rpm. Also, from memory, the standard gearing is around 17.5mph/1000 revs, so about 70mph at 4,000 rpm. Therefore, either your rev counter or speedo is out or have you changed the gearing?
 
Thanks for the comments, which justify me asking the original question.

Both gauges overhauled by Marcel last year, speedo seems about right when compared to other traffic and speed warning cameras. Rev counter nice and smooth. Tick over steady 1700.

The engine has been totally rebuilt, no mention of any racing mods!

Ged has set the engine to 30 degrees , I’m not sure which DMC curve, will have to check

Appreciate any more information
 
Tickover a steady 1700? :eek:

Should be a steady 800-1000 max with a healthy engine. Stock cams should yield 800-900 easy, with correct ignition and carb settings. Lumpier C4 Jota cams like a tad more, closer to 1000rpm.

piet
 
Sounds like the rev counter is miles out. If not you have a bundle of other trouble. Was it the CB750 rev counter that looked similar but had a different ratio?
 
no question about it 5000 rpm should give you around 90MPH.
I have spent a lot of time in that town, during my 44 years and 250,000+ kilometres
CLEM
 
Yes- 1700 way too high an idle, so either your carbs need adjusting/synching or the timing is off. Does the engine sound like it's racing at this idle? The needed high rev takeoff could indicate clutch issues, so check the cable freeplay (unless it's hydraulic). It should easily break 100 mph.
 
Use a tach like mechanics do....a diagnostic tool, some timing lights have them or even a cheap standalone aftermarket tach meant for a car or a boat etc. Typically they connect to a your battery positive side, a 12v negative coil wire and the corresponding high tension spark plug wire. Depending on your coils and ignition and tach you are using you may need to switch the number of cylinders it is reading to get a signal for only one cylinder...only some aftermarket car/boat/ motorcycle tachs have a switch to go this, in my limited experience the diagnostic tool/timing light type tachs will get the right reading for just one cylinder.

Seat of the pants....1000 rpm or so is a steady slow rpm....much slower it will get irratic and soon stall. 1700 rpm the engine will be singing a bit....loud and higher frequency vibration. You can turn the idle down and it will keep running smooth as long as carbs, timing, plugs and high tension leads and caps are good.
 
Help somewhat if you can describe what happens, at initial ride off, select first gear, no clutch drag? Some low throttle application, clutch out, what happens then? May seem silly or obvious questions, though easy things first. An easy idle is obvious ( 900rpm or so ) to a 1700 "idle" will be uncomfortable to the ear. Unlikely the lads whom rebuilt the engine would let it out with what you describe. May well be a fueling issue days end, consequence of getting the bike home and a few rides that allowed contamination(s) to circulate, water or solids. Perhaps contaminated fuel from refuelling stop? HTH j
 
The idle sounds fine, I mean it doesn’t sound too high, as you say, Ged at GCS would not let it go with such an obvious issue.

You mention solids, I did notice debris in one of the clear fuel lines after the first 100miles but by the time I got home and planned to clear the line , it had gone, nothing in the float bowl drain plug either.

First gear, I have to run up the revs from what I read as “1700” to about 3000 before slipping the clutch out, then she takes off nice and smooth, really goes from 4000. Maybe it is a tacho calibration issue, but I still have run up the revs from tick over to get her going. When I’m driving country roads ,it’s great so long as I keep above 4000.
 
Check choke cables for a hang up somewhere.
Mtoliva said:
The idle sounds fine, I mean it doesn’t sound too high, as you say, Ged at GCS would not let it go with such an obvious issue.

You mention solids, I did notice debris in one of the clear fuel lines after the first 100miles but by the time I got home and planned to clear the line , it had gone, nothing in the float bowl drain plug either.

First gear, I have to run up the revs from what I read as “1700” to about 3000 before slipping the clutch out, then she takes off nice and smooth, really goes from 4000. Maybe it is a tacho calibration issue, but I still have run up the revs from tick over to get her going. When I’m driving country roads ,it’s great so long as I keep above 4000.
Click to expand...
 
May well be the most effective process to return or call to the business that rebuilt the motor and have a chat with them, for next best action and diagnosis. Not usual what your describing for excessive rpm to achieve mobility. Could proffer various ( as others with many years experiences ), better aspect is that it did run properly at the workshop, a good base reference for diagnosing any issues. HTH J
 
Certainly Ged or Keith would be worth talking to. Also - shoot a video clip of tickover and take off to post here.
Mtoliva said:
I did notice debris in one of the clear fuel lines after the first 100miles but by the time I got home and planned to clear the line , it had gone, nothing in the float bowl drain plug either.
Click to expand...
Debris could be blocking pilot circuit
 
Last edited:
You must log in or register to reply here.
Back
Top