15-04-2011, 04:58 PM
Hi Andy,
Nice bike you have. I owned two R75/5's in 1972/3 the first second hand the second brand new.
Given the amount of bad weather have you tried spraying the electrics with WD40?
Have a look at the points as these can close up; my new bike started to play up and became quite lethal; it would only run on one cylinder until it hit around 3,000 revs then it would clear its throat almost pulling my arms off; on one occasion riding through Dewsbury on a busy market day I was cranked into a bend when it fired on both cylinders lifting the front wheel changing direction almost hitting a pedestrian.
I booked it in under warranty and it was checked over in the workshops by the top mechanic; on the way home the problem appeared again so in desperation I returned once again to the dealer to be told it must be the diaphragms in the Bing carbs so new diaphragm units were ordered. I went over once these arrived and the mechanic was on holiday but as I have rebuilt many bikes I was allowed to bring the new parts home and fit them myself. After fitting the parts the bike fired flames out of the exhaust so obviously the original fault remained. The bike was still under warranty and at that time cost as much as a terrace house to buy so I was rather timid of playing with it but decided to have a go.
I removed the front engine cover to gain access to the ignition points and found I could not insert a two thou feeler gauge whilst turning the engine to where the points should be fully open. I adjusted the points and the bike ran perfectly for the rest of the time I owned it.
What age is your bike Andy and what mileage has it covered. You might think the fault to be something complicated when in fact it might be something very simple being something out of adjustment.
What is the performance like when it does run; I know you won't take it over 70mph but what is it like at the end of the throttle cable; is the performance there if it is then this rules out a lot of the major problems like worn bores; pistons; valves or even broken rings.
Have you done all the basic checks like engine timing; tappets and points etc? is the air filter clean?
I used to work on the very first Honda bikes imported into the country and a friend bought a 175cc which ran perfectly like your bike whilst warm but then it would not start once it cooled overnight without new spark plugs being fitted; again this was another bike under warranty so it kept going back and each time it was fitted with new plugs it ran perfectly.
The problem became so bad that the dealer would send his daughter out with a pair of plugs but the fault could not be found. I ended up pulling the engine out and stripped it right down to its crankcase; I checked everything but all was in order and I could not find the slightest fault so I re-assembled the bike and wrote to Honda explaining the problem and what I had done so far; the bike had been bought from a different dealer to which I worked for.
I received a lovely letter from Honda with an apology asking me to change the air filter; the bike ran perfectly with a new air filter fitted starting easily from either hot or cold.
I used to balance the carbs on my BMW's using a vacuum gauge but then I was keen.
Two bikes I owned that were huge disappointments were an Ariel 1,000cc Square Four that broke one rear con rod and shattered two pistons whilst plodding up the M6 at a steady 70mph; I scrapped the bike after that. The second was a Norton 750cc Atlas that would break its piston skirts every time it was taken up to 110mph; the best thing that happened to that bike was to be hit head on by a lunatic driving with all his windows iced up in the middle of winter fracturing both my legs.
We are a knowledgeable bunch on this forum. By the way my rear tyre only used to last 4,000 miles on my BMW's, I was running TT 100's.
I hope my ramblings are of use but got to knock off as it's tea time.
Good luck Andy and kind regards, Col
Nice bike you have. I owned two R75/5's in 1972/3 the first second hand the second brand new.
Given the amount of bad weather have you tried spraying the electrics with WD40?
Have a look at the points as these can close up; my new bike started to play up and became quite lethal; it would only run on one cylinder until it hit around 3,000 revs then it would clear its throat almost pulling my arms off; on one occasion riding through Dewsbury on a busy market day I was cranked into a bend when it fired on both cylinders lifting the front wheel changing direction almost hitting a pedestrian.
I booked it in under warranty and it was checked over in the workshops by the top mechanic; on the way home the problem appeared again so in desperation I returned once again to the dealer to be told it must be the diaphragms in the Bing carbs so new diaphragm units were ordered. I went over once these arrived and the mechanic was on holiday but as I have rebuilt many bikes I was allowed to bring the new parts home and fit them myself. After fitting the parts the bike fired flames out of the exhaust so obviously the original fault remained. The bike was still under warranty and at that time cost as much as a terrace house to buy so I was rather timid of playing with it but decided to have a go.
I removed the front engine cover to gain access to the ignition points and found I could not insert a two thou feeler gauge whilst turning the engine to where the points should be fully open. I adjusted the points and the bike ran perfectly for the rest of the time I owned it.
What age is your bike Andy and what mileage has it covered. You might think the fault to be something complicated when in fact it might be something very simple being something out of adjustment.
What is the performance like when it does run; I know you won't take it over 70mph but what is it like at the end of the throttle cable; is the performance there if it is then this rules out a lot of the major problems like worn bores; pistons; valves or even broken rings.
Have you done all the basic checks like engine timing; tappets and points etc? is the air filter clean?
I used to work on the very first Honda bikes imported into the country and a friend bought a 175cc which ran perfectly like your bike whilst warm but then it would not start once it cooled overnight without new spark plugs being fitted; again this was another bike under warranty so it kept going back and each time it was fitted with new plugs it ran perfectly.
The problem became so bad that the dealer would send his daughter out with a pair of plugs but the fault could not be found. I ended up pulling the engine out and stripped it right down to its crankcase; I checked everything but all was in order and I could not find the slightest fault so I re-assembled the bike and wrote to Honda explaining the problem and what I had done so far; the bike had been bought from a different dealer to which I worked for.
I received a lovely letter from Honda with an apology asking me to change the air filter; the bike ran perfectly with a new air filter fitted starting easily from either hot or cold.
I used to balance the carbs on my BMW's using a vacuum gauge but then I was keen.
Two bikes I owned that were huge disappointments were an Ariel 1,000cc Square Four that broke one rear con rod and shattered two pistons whilst plodding up the M6 at a steady 70mph; I scrapped the bike after that. The second was a Norton 750cc Atlas that would break its piston skirts every time it was taken up to 110mph; the best thing that happened to that bike was to be hit head on by a lunatic driving with all his windows iced up in the middle of winter fracturing both my legs.
We are a knowledgeable bunch on this forum. By the way my rear tyre only used to last 4,000 miles on my BMW's, I was running TT 100's.
I hope my ramblings are of use but got to knock off as it's tea time.
Good luck Andy and kind regards, Col
